SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 6-K

REPORT OF FOREIGN ISSUER
PURSUANT TO RULE 13a-16 OR 15d-16 OF THE

SECURITIES EXCHANGE ACT OF 1934

For March, 2026

(Commission File No. 1-31317)

Companhia de Saneamento Básico do Estado de São Paulo - SABESP

(Exact name of registrant as specified in its charter)

Basic Sanitation Company of the State of Sao Paulo - SABESP

(Translation of Registrant's name into English)

Rua Costa Carvalho, 300
São Paulo, S.P., 05429-900
Federative Republic of Brazil

(Address of Registrant's principal executive offices)

Indicate by check mark whether the registrant files or will file
annual reports under cover Form 20-F or Form 40-F.

Form 20-F ___X___ Form 40-F ______

Indicate by check mark if the registrant is submitting the Form 6-K
in paper as permitted by Regulation S-T Rule 101(b)(1)__.

Indicate by check mark if the registrant is submitting the Form 6-K
in paper as permitted by Regulation S-T Rule 101(b)(7)__.

Indicate by check mark whether the registrant by furnishing the
information contained in this Form is also thereby furnishing the
information to the Commission pursuant to Rule 12g3-2(b) under
the Securities Exchange Act of 1934.

Yes ______ No ___X___

If "Yes" is marked, indicated below the file number assigned to the
registrant in connection with Rule 12g3-2(b):

~~COMPANHIA~~Companhia DEde ~~SANEAMENTO~~Saneamento ~~BÁSICO~~Básico ~~DO ESTADO~~do DEEstado ~~SÃO~~de ~~PAULO~~São Paulo – SABESP

~~PUBLICLY-HELD~~Financial ~~COMPANY~~Statements as of

~~CNPJ~~December ~~43.776.517/0001-80~~31, 2025 and 2024

~~NIRE~~Companhia nºde ~~35.3000.1683-1~~Saneamento Básico do Estado de São Paulo – SABESP

~~MATERIAL~~Table ~~FACT~~of Contents of the 2025 Financial Statements

Companhia de Saneamento Básico do Estado de São Paulo – Sabesp (the "Company"), in compliance with the provisions of Resolution No. 44 of the Brazilian Securities and Exchange Commission ("CVM"), dated August 23, 2021, as amended, and as a continuation of the material facts disclosed on October 5, 2025 and January 20, 2026, hereby informs its shareholders and the market in general, at this date, that it has entered into a quota purchase and sale agreement and other covenants with África Fundo de Investimento Multimercado Responsabilidade Limitada for the acquisition, by the Company, of 100% (one hundred percent) of the quotas of Oceania Fundo de Investimento em Ações ("Oceania") for the amount of R$ 171,637,858.05 (one hundred seventy-one million, six hundred thirty-seven thousand, eight hundred fifty-eight reais and five centavos).


Independent Auditor’s Report on Individual and Consolidated Financial Statements			F-3
Management Report			F-10
Statements of Financial Position			F-15
Statement of Income			F-17
Statement of Comprehensive Income			F-18
Statement of Changes in Equity			F-19
Statement of Cash Flows			F-20
Statement of Value Added			F-21
Notes to the Financial Statements			F-22
	1.	Operations
	2.	Basis of preparation and presentation of the financial statements
	3.	Material accounting policy information
	4.	Changes in accounting practices and disclosures
	5.	Risk management
	6.	Significant accounting estimates and judgments
	7.	Cash and cash equivalents
	8.	Financial investments
	9.	Restricted cash
	10.	Trade receivables
	11.	Related-party balances and transactions
	12.	Investments
	13.	Contract assets
	14.	Intangible assets and other concession assets
	15.	Financial Asset of the Concession
	16.	Property, plant, and equipment
	17.	Borrowings and financing
	18.	Financial instruments
	19.	Derivative financial instruments and hedging transactions
	20.	Taxes and Contributions
	21.	Deferred PIS/Cofins taxes
	22.	Deferred taxes and contributions
	23.	Provisions
	24.	Labor and social obligations
	25.	Pension plan obligations
	26.	Services payable
	27.	Equity
	28.	Earnings per share
	29.	Operating segment information
	30.	Operating revenue
	31.	Operating costs and expenses
	32.	Financial income, net
	33.	Other operating income (expenses), net
	34.	Commitments
	35.	Supplemental cash flow information
	36.	Events after the reporting period
Executive Officers’ Statement			F-106
Fiscal Council’s Opinion			F-108
Summary Annual Report of the Statutory Audit Committee			F-109

~~Oceania's sole asset consists of 3,407,000 (three million, four hundred and seven thousand) registered, book~~F-entry common shares with no par value issued by EMAE – Empresa Metropolitana de Águas e Energia S.A. ("EMAE"), representing 23.17% (twenty-three point seventeen percent) of EMAE's common shares and 9.22% (nine point twenty-two percent) of EMAE's total share capital.2

~~The~~A ~~acquisition~~free ~~price~~translation ~~shall~~from bePortuguese ~~paid~~into inEnglish ~~cash on~~of ~~March~~Independent ~~13,~~Auditor’s Report ~~2026,~~on ~~and~~financial isstatements ~~not~~prepared ~~subject~~in toBrazilian ~~subsequent~~currency ~~adjustments.~~in ~~The~~accordance ~~price~~with ~~corresponds to~~ the ~~price~~accounting ~~per~~practices ~~share~~adopted ~~offered~~ in ~~connection~~Brazil ~~with the~~and ~~public tender offer for~~ the ~~acquisition~~International Financial ofReporting ~~EMAE's~~Standards ~~common shares~~ (~~i.e., R$49.47 (forty-nine reais and forty-seven centavos~~IFRS) ~~per~~issued ~~share), registered with the CVM, pursuant to Article 254-A of Law No. 6,404, dated December 15, 1976, duly adjusted~~ by the ~~SELIC~~International ~~rate~~Accounting ~~until~~Standards ~~March 11,~~Board ~~2026, through the present date, which results in a price per EMAE share of R$50.38~~ (~~fifty reais and thirty-eight centavos~~IASB).

~~The~~Independent ~~Company~~auditor’s ~~will~~report ~~keep~~on ~~its~~individual ~~shareholders~~ and ~~the~~ ~~market~~consolidated ~~in general informed of any developments related to the subject matter of this Material Fact.~~financial statements

~~São~~The ~~Paulo~~Shareholders, ~~March~~Board ~~12,~~of ~~2026~~Directors and Officers

~~DANIEL~~Companhia ~~SZLAK~~de Saneamento Básico do Estado de São Paulo - SABESP

Opinion

We have audited the individual and consolidated financial statements of Companhia de Saneamento Básico do Estado de São Paulo - SABESP (the “Company”), identified as individual and consolidated, respectively, which comprise the statement of financial position as at December 31, 2025 and the statements of income, of comprehensive income, of changes in equity, and of cash flows for the year then ended, and the notes to the financial statements, including material accounting policies and other explanatory information.

In our opinion, the accompanying individual and consolidated financial statements present fairly, in all material respects, the Company’s individual and consolidated financial position as at December 31, 2025, its individual and consolidated financial performance and its individual and consolidated cash flows for the year then ended, in accordance with the accounting practices adopted in Brazil and the International Financial Reporting Standards (IFRS) issued by the International Accounting Standards Board (IASB).

Basis for opinion

We conducted our audit in accordance with the Brazilian and International Standards on Auditing. Our responsibilities under those standards are further described in the “Auditor’s responsibilities for the audit of the individual and consolidated financial statements” section of our report. We are independent of the Company and its subsidiaries in accordance with the relevant ethical principles set forth in the Code of Professional Ethics for Accountants and the professional standards issued by Brazil’s National Association of State Boards of Accountancy (CFC), applicable to audits of financial statements in Brazil, and we have fulfilled our other ethical responsibilities in accordance with these requirements. We believe that the audit evidence we have obtained is sufficient and appropriate to provide a basis for our opinion.


	F-3

Key audit matters

Key audit matters are those matters that, in our professional judgment, were of most significance in our audit of the financial statements of the current year. These matters were addressed in the context of our audit of the individual and consolidated financial statements as a whole, and in forming our opinion thereon, and we do not provide a separate opinion on these matters. For each matter below, a description of how our audit addressed the matter, including any commentary on the findings or outcome of our procedures, is provided in the context of the financial statements taken as a whole.

We have fulfilled the responsibilities described in the “Auditor’s responsibilities for the audit of the individual and consolidated financial statements” section of our report, including in relation to these key audit matters. Accordingly, our audit included the performance of procedures designed to respond to our assessment of the risks of material misstatement of the financial statements. The results of our audit procedures, including the procedures performed to address the matters below, provide the basis for our audit opinion on the accompanying financial statements.

Contract Asset Related to Service Concession Agreements

As mentioned in Note 13 to the individual and consolidated financial statements, in the year ended December 31, 2025, the Contract Asset related to service concession agreements is recognized at fair value during the construction period. This Contract Asset represent the right to consideration in exchange for goods or services transferred to the customer under the existing service concession agreements. The expenditures incurred on the infrastructure serving the concession are an essential component of the methodology applied by the granting authority for determining the tariff to be charged to end consumers and the indemnification to be received by the Company upon termination of the service concession agreements. As disclosed in Note 13 (i), additions to Contract Assets for the year amounted to R$14,430,593 thousand in the individual financial statements and R$14,437,363 thousand in the consolidated financial statements.

These transactions recognized in Contract Assets involve material amounts, are decentralized across various municipalities/projects, involve high transaction volumes, and require judgment in determining which expenditures qualify as investments in concession infrastructure that will be eligible for capitalization. Therefore, we considered this to be a key audit matter.


	F-4

How our audit addressed this matter

Our audit procedures on concession-related Contract Assets included, among others, analyzing the nature of expenditures incurred in the construction of infrastructure during the year, analyzing their adherence to the terms of the existing service concession agreements and the applicable accounting standards; reviewing the supplier base and selecting samples for detailed testing of suppliers with the highest transaction volumes (by value or recurrence) during the year, applying unpredictability criteria to our sampling; evaluating the competence and reputation of key suppliers through media research, restrictive lists, and registration status; conducting field inspections of ongoing construction works, selected based on relevance and unpredictability criteria, to verify the existence of assets/infrastructure under construction; obtaining external confirmations from suppliers with the highest transaction volumes during the year (by value or recurrence); performing tests on journal entries, reviewing debits in the contract asset account against matching entries that were inconsistent with the nature of the transaction; and assessing the adequacy of the disclosures in the corresponding notes to the individual and consolidated financial statements as at December 31, 2025.

Based on the outcome of our audit procedures performed on the Contract Assets related to the service concession agreements, which are consistent with the executive board’s assessment, we consider that the criteria and assumptions adopted by the executive board, as well as the respective disclosures in Note 13, are acceptable in the context of the financial statements taken as a whole.

Revenue from sanitation services

As mentioned in Note 30 to the individual and consolidated financial statements, in the year ended December 31, 2025, revenue from the provision of water supply and sewage services, which comprises individual and consolidated net operating revenue, are recognized based on water consumption or on the rendering of services, it also includes unbilled revenue, which represents revenue incurred for services rendered but not billed by year-end, and are recognized based on estimates. These revenues involve highly dispersed and high-volume transactions, and in addition, measuring unbilled revenue involves the executive board’s judgment, considering the estimates required to identify and measure the volume of water supply and sewage services provided but not billed at year-end. Therefore, we considered this to be a key audit matter.


	F-5

How our audit addressed this matter

Our audit procedures on revenue from sanitation services included, among others, performing correlation tests on journal entries among revenue, accounts receivable, and cash accounts; carrying out anchor testing on cash inflows utilized to settle accounts receivable; performing cut-off procedures, including reviewing transactions close to year end; analyzing changes in revenue, accounts receivable, and cash through substantive analytical procedures; testing debt balances recorded in revenue accounts, analyzing any transactions lacking matching entries consistent with the nature of the Company’s operations and business; performing substantive analytical procedures on unbilled revenue and recalculating a sample of invoices; as well as assessing the adequacy of the disclosures in the corresponding notes to the individual and consolidated financial statements as at December 31, 2025.

Based on the outcome of our audit procedures on revenue from sanitation services, which is consistent with the executive board’s assessment, we consider that the criteria and estimates adopted by the executive board, as well as the respective disclosures in Note 30 are acceptable in the context of the financial statements taken as a whole.

Other matters

Audit of corresponding figures

The Company’s financial statements for the year ended December 31, 2024 were audited by another independent auditor, who issued an unmodified audit report dated March 24, 2025.

Statements of value added

The individual and consolidated statements of value added (SVA) for the year ended December 31, 2025, prepared under the responsibility of Company’s executive board, and presented as supplementary information for the purposes of IFRS, were submitted to audit procedures conducted together with the audit of the Company’s individual and consolidated financial statements. To form our opinion, we evaluated if these statements are reconciled with the financial statements and accounting records, as applicable, and if their form and content comply with the criteria defined by Accounting Pronouncement CPC 09 – Statement of Value Added. In our opinion, these individual and consolidated statements of value added have been properly prepared, in all material respects, in accordance with the criteria set forth in this Accounting Pronouncement and are consistent with the individual and consolidated financial statements taken as a whole.


	F-6

Other information accompanying the individual and consolidated financial statements and the auditor’s report

The executive board is responsible for such other information, which comprises the Management Report.

Our opinion on the individual and consolidated financial statements does not cover the Management Report, and we do not express any form of assurance conclusion thereon.

In connection with our audit of the individual and consolidated financial statements, our responsibility is to read the Management Report and, in doing so, consider whether this report is materially inconsistent with the financial statements or our knowledge obtained in the audit or otherwise appears to be materially misstated. If, based on the work we have performed, we conclude that there is a material misstatement of the Management Report, we are required to report that fact. We have nothing to report in this respect.

Responsibilities of the executive board and those charged with governance for the individual and consolidated financial statements

The executive board is responsible for the preparation and fair presentation of the individual and consolidated financial statements in accordance with the accounting practices adopted in Brazil and with the International Financial Reporting Standards (IFRS) issued by the International Accounting Standards Board (IASB), and for such internal control as the executive board determines is necessary to enable the preparation of financial statements that are free from material misstatement, whether due to fraud or error.

In preparing the individual and consolidated financial statements, the executive board is responsible for assessing the Company’s ability to continue as a going concern, disclosing, as applicable, matters related to going concern and using the going concern basis of accounting unless the executive board either intends to liquidate the Company or to cease operations, or has no realistic alternative but to do so.

Those charged with governance are responsible for overseeing the Company’s and its subsidiaries’ financial reporting process.

Auditor’s responsibilities for the audit of the individual and consolidated financial statements

Our objectives are to obtain reasonable assurance about whether the individual and consolidated financial statements as a whole are free from material misstatement, whether due to fraud or error, and to issue an auditor’s report that includes our opinion. Reasonable assurance is a high level of assurance but is not a guarantee that an audit conducted in accordance with the Brazilian and International Standards on Auditing will always detect a material misstatement when it exists. Misstatements can arise from fraud or error and are considered material if they could, individually or as a whole, reasonably be expected to influence the economic decisions of users made on the basis of these financial statements.


	F-7

As part of an audit in accordance with the Brazilian and International Standards on Auditing, we exercise professional judgment and maintain professional skepticism throughout the audit. We also:

Identify and assess the risks of material misstatement of the individual and consolidated financial statements, whether due to fraud or error, design and perform audit procedures responsive to those risks, and obtain audit evidence that is sufficient and appropriate to provide a basis for our opinion. The risk of not detecting a material misstatement resulting from fraud is higher than for one resulting from error, as fraud may involve collusion, forgery, intentional omissions, misrepresentations, or the override of internal control.

Obtain an understanding of internal control relevant to the audit in order to design audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of the Company’s and its subsidiaries’ internal control.

Evaluate the appropriateness of accounting policies used and the reasonableness of accounting estimates and related disclosures made by the executive board.

Conclude on the appropriateness of the executive board’s use of the going concern basis of accounting and, based on the audit evidence obtained, whether a material uncertainty exists related to events or conditions that may cast significant doubt on the Company’s ability to continue as a going concern. If we conclude that a material uncertainty exists, then we are required to draw attention in our auditors’ report to the related disclosures in the individual and consolidated financial statements or, if such disclosures are inadequate, to modify our opinion.Our conclusions are based on the audit evidence obtained up to the date of our auditors’ report. However, future events or conditions may cause the Company to cease to continue as a going concern.

Evaluate the overall presentation, structure and content of the financial statements, including the disclosures, and whether the individual and consolidated financial statements represent the underlying transactions and events in a manner that achieves fair presentation.

We communicate with those charged with governance regarding, among other matters, the planned scope and timing of the audit and significant audit findings, including any significant deficiencies in internal control that we identify during our audit.

We also provide those charged with governance with a statement that we comply with relevant ethical requirements, including those regarding independence, and communicate with them all relationships and other matters that may reasonably be thought to bear on our independence, and where applicable, the actions taken to eliminate threats, or the safeguards applied.


	F-8

From the matters communicated with those charged with governance, we determined those matters that were of most significance in the audit of the financial statements of the current year and are therefore the key audit matters. We describe these matters in our auditor’s report unless law or regulation precludes public disclosure about the matter or when, in extremely rare circumstances, we determine that a matter should not be communicated in our report because the adverse consequences of doing so would reasonably be expected to outweigh the public interest benefits of such communication.

São Paulo, March 16, 2026.

ERNST & YOUNG

Auditores Independentes S/S Ltda.

CRC SP-034519/O

Original report in Portuguese signed by

Uilian Dias Castro de Oliveira

Accountant CRC SP-223185/O


	F-9

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Management Report

2025 marked the first full cycle following Sabesp’s privatization and consolidated a period of significant transformation for the Company. We advanced with speed, discipline, and consistency, delivering concrete results and strictly executing our universalization plan.

Our conduct was driven by three central priorities:(i) full compliance with the requirements of the new concession agreement (new water and sewage units and service quality indicators), accelerating investments aimed at universalization and strengthening adherence to the regulatory framework; (ii) improving operational and commercial efficiency, increasing standards of quality, reliability, and customer service; and (iii) strengthening financial efficiency and corporate governance across people, processes, and technology.

Throughout the year, we invested R$ 15.2 billion in water supply and sewage infrastructure, surpassing all U-Factor targets for the 2024-2025 cycle. This included achieving 152% of the Water Units target, 133% of the Sewage Units target, and 134% of the Units for Sewage Treatment target. These investments brought health, dignity, and quality of life to approximately 1.8 million people who received access to treated water, 2.1 million who received sewage collection services, and 3.8 million individuals who now have their sewage treated. Additionally, we supported the local economy by generating more than 40,000 direct and indirect jobs during the year.

From an operational standpoint, we achieved significant results, with a 2-point increase in the NPS (Net Promoter Score) compared to 2024, demonstrating continuous improvement in customer experience. We modernized our metering infrastructure, installing approximately 1.5 million new meters this year, while simultaneously securing a contract for what will be the world's largest smart metering project in the water sector: 4.4 million IoT-enabled meters by 2029, supported by R$ 3.8 billion in already contracted investments.

On the corporate front, we advanced the consolidation of the Sabesp’s New Culture and made progress in the ‘Sabesp Gente’ program by welcoming 120 interns, 380 apprentices, and launching our first trainee program, selecting 22 new talents. We optimized our workforce, closing the year with 9,204 employees, a reduction of 13% compared to December 2024. We also completed the first full cycle of Zero-Based Budgeting, redesigning accounts and cost centers and reinforcing our internal governance and budget discipline.

In terms of sustainability, 2025 represents a leap in ambition. We formalized our decarbonization roadmap for 2035, establishing robust targets for absolute and relative reductions in greenhouse gas emissions (41%), even in a context of significant expansion of the volume of sewage treated, in line with universalization goals. As a result, we were honored with recognition from CDP, improving our rating from "C" to "B".

We continue to look to the future with responsibility, urgency, and long-term vision. The acquisition of EMAE represented a decisive step toward strengthening medium and long-term water security. With the Billings reservoir, we will be able to increase our water storage capacity by 52% and integrate essential water and energy assets, generating synergies with structuring programs such as Integra Tietê, which seeks to expand capacity, increase inter-basin transfers, and strengthen resilience to climate variability. In parallel, we expanded our energy transition strategy with self-generation projects totaling 186 MWm, reinforcing financial sustainability, reducing emissions, and increasing predictability in energy costs.

These advances demonstrate how Sabesp is preparing to operate with greater efficiency, resilience, and positive impact in the coming decades, combining structural investments, operational modernization, and strengthened governance. We thank all our stakeholders, including employees, partners, regulators, customers, suppliers, investors, and the communities we serve, for their support, trust, and continuous engagement throughout this transformation.

COMPANY OVERVIEW

Sabesp’s purpose is to connect people to a better future by delivering essential services with excellence and with a strong commitment to public health and environmental preservation. We are one of the largest sanitation companies in the world by number of customers, serving approximately 30 million people with water supply services and 27 million people with sewage collection and treatment services in 2025.


	F-10

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

In addition to operating directly in 375 municipalities, the Company holds minority stakes in three companies that provide water supply and sewage collection and treatment services, as well as six other companies that operate in the energy, paving, and sanitation-related services sectors. Detailed information on these investee companies is presented in Note 12 to the 2025 Financial Statements.

The Company’s shares are listed on the “Novo Mercado” segment of B3 under the ticker “SBSP3” since April 2002, and on the New York Stock Exchange “NYSE”, in the form of Level III American Depositary Receipts “ADRs”, under the ticker “SBS” since May 2002.

PEOPLE AND CULTURE

In 2025, Sabesp advanced in consolidating a New Culture, reinforcing the Company’s identity and supporting the transformations underway. This process was developed through extensive internal listening and analysis, aligning the purpose of connecting people to a better future with practices that ensure operational excellence, socio-environmental responsibility, and positive impact for society.

The New Culture resulted from the active participation of multiple areas and organizational levels, establishing guiding principles that shape our actions: customer focus, trust-based collaboration, ownership with a holistic view, ethics, and purpose-driven execution. More than values, these principles reinforce alignment between strategy and behavior and support a more modern and agile Sabesp, prepared for the challenges of our sector.

In people management, the “Sabesp Gente” Program supported this cultural journey through initiatives aimed at talent attraction, workforce renewal, and sustainable workforce management. In 2025, the Company hired 120 interns, 380 apprentices, and launched its first trainee program, selecting 22 new talents. Sabesp also implemented a new Voluntary Dismissal Program (PDV) to support career transitions. These actions combine the experience of the technical workforce with the energy of new generations, strengthening the Company’s execution capacity throughout the universalization cycle.

Through the New Culture and “Sabesp Gente”, we reinforce an environment where desired behaviors are recognized, talent has opportunities to grow, and decisions are guided by purpose, ethics, and responsibility toward people and future generations. This cultural foundation is essential to ensure that Sabesp continues to advance consistently, aligning operational excellence, sustainability, and the development of its human capital.

SUSTAINABILITY

Sabesp’s ESG strategy advanced significantly in 2025. Under the climate pillar, the Company formalized emission-reduction targets through 2035: (i) 41% reduction in emissions intensity (tCO₂/ ‘000m³ of treated sewage), (ii) 15% reduction in combined total emissions from Scopes 1, 2, and 3, and (iii) 43% reduction in Scope 2 emissions through self-generation and the purchase of clean energy. These targets were established alongside the expansion of treatment volumes, demonstrating that it is possible to grow while reducing carbon intensity.

To enable the energy transition, the Company executed long-term self-generation contracts with Casa dos Ventos (126 MWm) and Engie (60 MWm), in addition to 32 photovoltaic plants already commissioned, totaling 44 MWp in operation. These initiatives reduce costs, volatility, and emissions while strengthening business resilience.

Furthermore, at the Barueri, São Miguel, and Lavapés sewage treatment plants, the Company is advancing the implementation of solutions focused on reducing operating costs and increasing energy efficiency. Key initiatives include: (i) biogas utilization, enabling the generation and use of biogas produced onsite for power generation and for thermal sludge drying using heat from biogas combustion, and (ii) implementation of a sludge pipeline at the Parque Novo Mundo sewage treatment plant, replacing road transport with pipeline transport, which will reduce logistics costs, increase operational reliability, and significantly reduce the Company’s carbon footprint.

From a water-security and resilience perspective, Sabesp continues to strengthen the Integrated Metropolitan System through increased storage capacity, expanded capacity for transfers between systems, production-capacity expansion


	F-11

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

projects, and indirect water-reuse initiatives. By 2030, the Company expects to add at least 12.8 m³/s of capacity through retrofits, expansions, three indirect reuse projects, reactivation of the Billings–Taiaçupeba interconnection, and the Paraíba do Sul–Alto Tietê transfer, with estimated Capex of R$ 8.2 billion, anticipated from the second tariff cycle.

In governance and transparency, the Company achieved a CDP Climate score of B, an improvement compared to 2024, reflecting progress in managing climate-related risks and opportunities.

EXTERNAL AUDIT SERVICES

In the fiscal year ended December 31, 2025, the Company did not engage any services other than audit services from its external auditors.

ECONOMIC AND FINANCIAL PERFORMANCE

In 2025, Sabesp reached R$ 37.6 billion in net revenue (+4% vs. 2024) and R$ 8.5 billion in Net Income (-12% vs. 2024). It is important to note that, in 2024, the bifurcation of the financial asset generated a gain of approximately R$ 5.5 billion in the Company’s Net Income. Adjusting for the effect of financial asset remeasurement, the Company’s Net Income amounted to R$ 6.3 billion, an increase of 22% y/y. Finally, the Company announced the distribution of R$ 1.8 billion to its shareholders in IoE ("Interest on Equity").

Financial Asset Bifurcation (Indemnity)

In 2024, following the completion of the privatization process and the execution of the agreement with URAE-1 on July 23, 2024, the Company recognized the bifurcation of the financial asset related to concession assets, previously classified solely as intangible assets. The financial asset corresponds to reversible investments that are not fully amortized by the end of the contract term (October 2060), which will be indemnified as set forth in the URAE-1 agreement. The recognition of this financial asset generated the following impacts in 2024: R$ 9,161 million in gross revenue and R$ 5,481 million in net income. For further information, refer to Note 16 of the 2024 Financial Statements.

Net revenue from sanitation services increased 2.2% y/y in 2025, reaching R$ 22.2 billion, explained by:

· +3.7% in net price: removal of discounts to large clients (“Demanda Firme”);

· +2.4% in billed volume: growth in new units;

· (1.8)% in mix: increase in vulnerable customers eligible for subsidized tariffs (from 2.0 million to 3.2 million registered customers, annual average);

· (2.1)% FAUSP: in 2024 FAUSP began only in the second half of the year and the rate was revised in August 2025


	Billed Volume (million de m³)			Average Tariff (R$/m³)
Category	2025	2024	%	2025	2024	%
Residential	3,764	3,683	2.2	4.07	4.22	(3.4)
Commercial	396	386	2.4	14.78	14.28	3.5
Industrial	74	74	(0.2)	19.23	16.94	13.5
Total Retail	4,233	4,143	2.2	5.34	5.38	(0.8)
Wholesale	54	60	(10.1)	2.78	2.56	8.8
Other¹	120	113	6.3	18.15	18.87	(3.8)
Consolidated Total	4,407	4,316	2.1	5.66	5.70	(0.7)


	F-12

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

ADMINISTRATIVE COSTS AND EXPENSES

In 2025, costs and expenses reached R$ 11.2 billion, an improvement of 13.8% compared to 2024, mainly due to developments in the following lines: (i) general expenses (-54.5% y/y) related to advance transfers to municipal funds (FMSAI); (ii) general materials (-29.3% y/y) due to process standardization and contract reviews throughout the year; and (iii) personnel (-9.9% y/y) due to a 13% reduction in the workforce.”

INVESTMENTS

In 2025, capex totaled R$ 15,202 million, an increase of 120% compared to the same period of the previous year. By the end of the first tariff cycle, in 2029, the Company estimates approximately R$ 70 billion in investments to achieve the universalization of water supply and sewage services across the 371 municipalities that comprise URAE-1.


	2025	2024	Var. (R$)	%
Water	4,921	2,891	2,030	70.2
Sewage	10,280	4,020	6,260	155.7
Total	15,202	6,911	8,290	120.0

LEVERAGE AND CAPITAL STRUCTURE

In 2025, Sabesp issued R$ 18.7 billion in debt instruments to finance investments related to universalization. In addition, 2025 was focused on reducing the cost of debt, which closed the year at CDI – 0.20%, and on extending maturities, with an average debt maturity of 5.6 years at the end of 2025.

Even with the year’s borrowings, the Company’s Leverage Ratio increased only 5p.p. y/y, supported by strong cash generation during the period. The net debt/Adjusted EBITDA ratio ended the year at 2.2x, a healthy level for companies in the sector.


R$ million	As of December 31
	2025	2024
Total borrowings and financing (Gross Debt)	40,142	25,258
(-) Cash and cash equivalents	(4,663)	(1,683)
(-) Financial investments	(7,708)	(3,700)
(=) Net debt	27,771	19,876
(+) Total Equity	42,401	36,928
(=) Total Capital	70,172	56,804
Leverage Ratio	40%	35%

The Company believes that its capital structure is well suited to its operations and industry. Historically, these capitalization metrics have enabled the Company to access official and multilateral banks, manage current investment levels, and maintain a favorable debt profile, characterized by long-term, low-cost financing.

As of December 31, 2025, the Company’s equity reached R$ 42.4 billion (+15% vs. 2024). This increase was driven by retained earnings generated in 2025.


	F-13

Companhia de Saneamento Básico do Estado de São Paulo – SABESP


R$ million	As of December 31
	2025	2024
Providers of capital – current	5,093	3,134
Providers of capital – noncurrent	35,049	22,124
Shareholders – Equity	42,401	36,928
Total capitalization	82,543	62,186

PAYMENT OF INTEREST ON EQUITY (IoE)

On December 18, 2025, the Board of Directors approved the crediting of Interest on Equity in the total gross amount of R$ 1,798,000, corresponding to R$ 2.643892990 per share, to be paid on April 30, 2026, as per the Notice to the Market.

SHARES BUYBACK PROGRAM

On May 12, 2025, the Board of Directors approved the Share Repurchase Plan, authorizing the acquisition of up to 6,904,170 common shares (approximately 1% of the total, on a fully diluted basis) for a period of 18 months (from 05/13/2025 to 11/12/2026). The primary purpose of the program is to serve the Company’s long-term incentive plans (Restricted Shares and Performance Shares) approved on 04/29/2025, while also allowing the Company to hold shares in treasury for future cancellation or sale. On the date of approval, the Company’s share capital consisted of 683,509,868 common shares (and 1 golden share), with no treasury shares. Shares buyback were and will continue to be carried out on B3’s trading platform.

Based on the shareholding position as of December 31, 2025, the Company held: (a) 703,773,869 outstanding shares, as defined under Article 67 of CVM Resolution No. 80/22; and (b) 3,554,431 treasury shares, representing approximately 0.5% of the Company’s total outstanding shares.

CAPITAL INCREASE

At the same meeting held on December 18, 2025, the Board of Directors approved a capital increase in the amount of R$ 2,810,000, within the limit of the authorized capital, through the capitalization of part of the balance of profit reserves, with the issuance of 20,264,000 new common shares (registered, book-entry, and with no par value). These shares will be granted free of charge to shareholders at the ratio of 0.029646975 new share for each common share held as of the shareholding position on 12/23/2025, pursuant to Article 169 of Law 6,404/76. The capitalized profits relate to periods prior to 2024.


	F-14

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Statements of Financial Position as of December 31, 2025 and 2024

In thousands of reais

		Individual		Consolidated
	Note	December 31, 2025	December 31, 2024	December 31, 2025	December 31, 2024

Current Assets
Cash and cash equivalents	7	4,569,998	1,681,204	4,663,226	1,682,606
Financial investments	8	7,693,630	3,694,029	7,707,745	3,699,694
Trade receivables	10 (a)	4,406,829	3,887,952	4,413,449	3,894,557
Accounts receivable from related parties	11 (a)	276,282	319,514	276,388	319,546
Inventories		21,863	10,524	22,061	10,818
Restricted cash	9	9,575	37,715	9,575	37,715
Taxes Recoverable	20 (a)	1,295,237	800,797	1,295,310	800,811
Derivative financial instruments	19	-	67,440	-	67,440
Assets held for sale		26,864	-	26,864	-
Other assets		159,500	99,582	141,892	95,673
Total current assets		18,459,778	10,598,757	18,556,510	10,608,860

Non-Current Assets
Financial investments	8	-	769,057	-	769,057
Trade receivables	10 (a)	258,544	327,798	258,544	327,798
Accounts receivable from related parties	11 (a)	862,782	908,875	862,782	908,875
Escrow Deposits		120,021	139,222	120,021	139,222
Water and Basic Sanitation National Agency - ANA		2,250	1,993	2,250	1,993
Other assets		31,259	306,085	31,259	135,227
Investments	12	494,088	215,803	254,358	215,803
Investment properties		49,933	46,630	49,933	46,630
Contract assets and other concession assets	13	11,006,489	4,872,410	11,018,516	4,877,667
Financial asset of the concession	15	21,665,330	17,601,626	21,665,330	17,601,626
Intangible assets	14	50,354,751	44,628,468	50,492,473	44,771,124
Property, plant, and equipment	16	890,791	561,548	890,791	561,548
Total non-current assets		85,736,238	70,379,515	85,646,257	70,356,570

Total Assets		104,196,016	80,978,272	104,202,767	80,965,430

The accompanying notes are an integral part of these financial statements.


	F-15

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Statements of Financial Position as of December 31, 2025 and 2024

In thousands of reais

		Individual		Consolidated
	Note	December 31, 2025	December 31, 2024	December 31, 2025	December 31, 2024

Current Liabilities
Trade payables and contractors		2,398,445	768,371	2,400,046	766,609
Services payable	26	2,767,899	1,434,998	2,772,416	1,438,507
Borrowings and financing	17	5,132,890	3,133,850	5,092,816	3,133,850
Labor and social obligations	24	699,629	1,286,193	699,629	1,286,193
Taxes and contributions payable	20 (b)	614,078	589,110	615,592	591,271
Deferred PIS/Cofins taxes	21	89,049	-	89,049	-
Dividends and interest on capital payable	27 (c)	2,059,850	2,275,890	2,059,850	2,275,890
Provisions	23 (a)	1,370,013	1,546,184	1,370,013	1,546,185
Public-Private Partnership - PPP	14 (c)	469,687	452,323	469,687	452,323
Derivative financial instruments	19	521,832	-	661,421	-
Performance Agreements	14 (f)	120,776	287,109	120,776	287,109
Other liabilities		201,620	194,293	201,619	194,308
Total current liabilities		16,445,768	11,968,321	16,552,914	11,972,245

Non-Current Liabilities
Borrowings and financing	17	35,168,713	22,124,447	35,049,531	22,124,447
Deferred income and social contribution taxes	22 (a)	3,129,908	2,661,891	3,129,908	2,661,891
Deferred PIS/Cofins	21	1,191,916	1,117,804	1,191,916	1,117,804
Provisions	23 (a)	533,399	895,495	533,399	895,495
Pension plan obligations	25	2,140,161	1,931,145	2,140,161	1,931,145
Public-Private Partnership - PPP	14 (c)	2,856,008	2,853,896	2,856,008	2,853,896
Performance Agreements	14 (f)	6,151	137,441	6,151	137,441
Other liabilities		322,868	359,778	341,655	343,012
Total non-current liabilities		45,349,124	32,081,897	45,248,729	32,065,131

Total liabilities		61,794,892	44,050,218	61,801,643	44,037,376

Equity
Capital stock	27 (a)	21,210,000	15,000,000	21,210,000	15,000,000
Capital reserves	27 (d)	30,219	-	30,219	-
Earnings reserves		21,518,212	21,647,715	21,518,212	21,647,715
Treasury shares		(475,385)	-	(475,385)	-
Equity valuation adjustments		118,078	280,339	118,078	280,339

Total equity	27	42,401,124	36,928,054	42,401,124	36,928,054

Total Liabilities and Equity		104,196,016	80,978,272	104,202,767	80,965,430

The accompanying notes are an integral part of these financial statements.


	F-16

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Statements of Income for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

		Individual		Consolidated
	Note	2025	2024	2025	2024
Net operating revenue	30	38,049,567	36,106,921	38,092,050	36,145,477
Operating costs	31	(23,960,423)	(16,580,263)	(23,991,688)	(16,603,073)

Gross profit		14,089,144	19,526,658	14,100,362	19,542,404

Selling expenses	31	(742,111)	(916,404)	(743,276)	(917,589)
Allowance for doubtful accounts	10 (c)	(61,450)	(557,126)	(62,067)	(557,789)
Administrative expenses	31	(1,010,532)	(2,307,452)	(1,018,282)	(2,311,438)
Other operating income (expenses), net	33	273,071	(280,450)	274,731	(280,450)
Equity accounting	12	48,644	21,622	48,153	35,322

Profit from operations before financial income (expenses)		12,596,766	15,486,848	12,599,621	15,510,460

Financial income, net	32	(900,253)	(1,848,591)	(897,770)	(1,867,652)

Profit before income tax and social contribution		11,696,513	13,638,257	11,701,851	13,642,808

Income and social contribution taxes
Current	22 (c)	(2,736,903)	(1,298,097)	(2,742,241)	(1,302,648)
Deferred	22 (c)	(497,551)	(2,760,597)	(497,551)	(2,760,597)
		(3,234,454)	(4,058,694)	(3,239,792)	(4,063,245)

Profit for the period		8,462,059	9,579,563	8,462,059	9,579,563
Earnings per share - basic and diluted (in reais)	28	12.37	14.02	12.37	14.02

The accompanying notes are an integral part of these financial statements.


	F-17

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Statements of Comprehensive Income for the

Years ended December 31, 2025 and 2024

In thousands of reais

		Individual and Consolidated
	Note		2025	2024

Profit for the period			8,462,059	9,579,563
Items which will be subsequently reclassified to the income statement:			(162,261)	133,977
Retained earnings (accumulated losses) on cash flow hedge, net of taxes	20		8,350	(8,350)
Actuarial retained earnings (accumulated losses) on Defined Benefit Plans, net of taxes	25		(170,611)	142,327

Total comprehensive income for the period			8,299,798	9,713,540

The accompanying notes are an integral part of these financial statements.


	F-18

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Statement of Changes in Equity for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

				Earnings reserves
	Note	Capital Stock	Treasury shares	Capital reserve	Legal reserve	Investment reserve	Complementary minimum dividend	Retained Earnings/Accumulated Losses	Equity valuation adjustments	Total
Individual
Balances as of December 31, 2023		15,000,000	-	-	1,864,605	12,753,361	93,048	-	146,362	29,857,376
Profit for the period		-	-	-	-	-	-	9,579,563	-	9,579,563
Gains and losses on financlal instruments	19	-	-	-	-	-	-	-	(8,350)	(8,350)
Actuarial gains and (losses)	25	-	-	-	-	-	-	-	142,327	142,327
Total comprehensive income/(loss) for the period		-	-	-	-	-	-	9,579,563	133,977	9,713,540
Legal reserve	27 (d)	-	-	-	478,978	-	-	(478,978)	-	-
Interest on capital (R$ 2.28 per share)	27 (c)	-	-	-	-	-	-	(1,556,454)	-	(1,556,454)
Dividends for the year (R$ 1,05 per share)	27 (c)	-	-	-	-	-	-	(718,692)	-	(718,692)
Complementary minimum dividends of 2023, approved (R$ 0,14 per share)	27 (c)	-	-	-	-	-	(93,048)	-	-	(93,048)
Withholding income tax on interest on capital attributed as minimum mandatory dividends		-	-	-	-	-	-	(274,668)	-	(274,668)
Transfers to the investment reserve	27 (e)	-	-	-	-	6,550,771	-	(6,550,771)	-	-
Balance as of December 31, 2024		15,000,000	-	-	2,343,583	19,304,132	-	-	280,339	36,928,054
Individual and Consolidated
Profit for the period		-	-	-	-	-	-	8,462,059	-	8,462,059
Gains and losses on financlal instruments	19	-	-	-	-	-	-	-	8,350	8,350
Actuarial gains and (losses)	25	-	-	-	-	-	-	-	(170,611)	(170,611)
Total comprehensive income/(loss) for the period		-	-	-	-	-	-	8,462,059	(162,261)	8,299,798
Capital increase	27 (b)	6,210,000	-	-	-	(6,210,000)	-	-	-	-
Treasuty shares	27 (h)	-	(475,385)	-	-	-	-	-	-	(475,385)
Long-Term Incentive Plan	27 (i)	-	-	30,219	-	-	-	-	-	30,219
Set-up of Reserves	27 (d)	-	-	-	423,103	-	-	(423,103)	-	-
Interest on equity (December 19, 2025)	27 (c)	-	-	-	-	-	-	(1,528,300)	-	(1,528,300)
Withholding Income Tax (IRRF) on interest on equity assigned as mandatory minimum dividends (December 19, 2025)	27 (c)	-	-	-	-	-	-	(269,701)	-	(269,701)
Interest on equity	27 (c)	-	-	-	-	-	-	(481,439)	-	(481,439)
Withholding Income Tax (IRRF) on interest on equity assigned as mandatory minimum dividends	27 (c)	-	-	-	-	-	-	(102,122)	-	(102,122)
Transfers to investment reserve	27 (e)	-	-	-	-	5,657,394	-	(5,657,394)	-	-
Balances as of December 31, 2025		21,210,000	(475,385)	30,219	2,766,686	18,751,526	-	-	118,078	42,401,124

The accompanying notes are an integral part of these financial statements.


	F-19

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Statements of Cash Flows for the

Years ended December 31, 2025 and 2024

In thousands of reais (continued)

	Individual		Consolidated
	2025	2024		2025	2024
Cash flows from operating activities
Profit before income and social contribution taxes	11,696,513	13,638,257		11,701,851	13,642,808
Adjustments for reconciliation of net income:
Depreciation and amortization	2,203,829	2,671,709		2,208,762	2,676,642
Residual value of property, plant and equipment, intangible assets and investment properties written-off	162,120	171,173		162,121	171,173
Allowance for doubtful accounts	61,450	557,126		62,067	557,789
Provisions and inflation adjustments on provisions	(241,134)	801,179		(241,134)	801,179
Interest calculated on borrowings and financing payable	3,571,181	1,796,070		3,571,181	1,796,070
Inflation adjustment and exchange gains (losses) on borrowings and financing	-	528,935		-	528,935
Interest and inflation adjustments, net	(2,815,102)	(237,136)		(2,816,414)	(237,617)
Derivative Financial Instruments	123,880	(300,155)		123,880	(300,155)
Financial Charges from Customers	(420,949)	(437,811)		(420,962)	(437,811)
Construction Margin on Intangible Assets arising from Concession Agreements	-	(139,856)		-	(139,976)
Provision for Consent Decree (TAC), Knowledge Retention Program (KRP) and Incentivized Dismissal Program (IDP) and Voluntary Dismissal Program (VDP)	105,187	354,078		105,187	354,078
Equity Accounting	(48,644)	(21,622)		(48,153)	(35,322)
Interest and inflation adjustment (PPP)	499,968	589,330		499,968	589,330
Municipal Transfers	594,688	309,807		595,045	309,807
Pension plan obligations	175,778	161,505		175,778	161,505
Deferred PIS and Cofins on financial asset of the concession	179,084	822,482		179,084	822,482
Financial Asset of the concession - restatement	(1,676,434)	(9,151,310)		(1,676,434)	(9,151,310)
Other adjustments	(505,673)	108,901		(504,021)	108,901
	13,665,742	12,222,662		13,677,806	12,218,508
Changes in assets
Trade receivables	1,496,597	(438,376)		1,503,136	(442,312)
Related-party balances and transactions	221,875	(25,396)		221,801	(25,429)
Inventories	24,126	(13,546)		24,222	(13,785)
Taxes Recoverable	153,188	(306,152)		153,129	(306,163)
Escrow Deposits	26,359	50,547		19,201	50,547
Other assets	4,065	(98,576)		122,644	(2,668)

Changes in liabilities
Trade payables and contractors	(1,084,563)	(435,781)		(1,082,801)	(437,694)
Services payable	738,213	375,965		738,864	377,968
Labor and social obligations	(701,066)	77,973		(701,066)	77,973
Taxes and contributions payable	(521,684)	265,244		(522,780)	265,189
Deferred PIS/Cofins	(15,923)	131,225		(15,923)	131,225
Provisions	(297,133)	(185,932)		(297,134)	(185,932)
Pension plan obligations	(267,190)	(227,233)		(267,190)	(227,233)
Other liabilities	(16,226)	(261,739)		1,909	(335,726)
Cash generated from operations	13,426,380	11,130,885		13,575,818	11,144,468

Interest Paid	(2,696,320)	(1,976,694)		(2,696,320)	(1,976,694)
Income tax and social contribution paid	(2,513,494)	(1,760,367)		(2,518,383)	(1,763,206)

Net cash generated from operating activities	8,216,566	7,393,824		8,361,115	7,404,568

Cash flows from financing activities
Acquisition of contract assets, intangible assets and property, plant and equipment	(13,735,223)	(8,025,537)		(13,740,392)	(8,030,674)
Restricted cash	(27,509)	17,229		(27,509)	17,229
Financial investments - Investment	(32,738,538)	(6,438,036)		(32,763,101)	(6,456,564)
Financial investments - Redemption	30,809,403	5,289,481		30,826,828	5,303,658
Financial investments - Noncurrent	-	(769,057)		-	(769,057)
Dividends received	16,945	-		16,945	-
Capital increase in investees	(102,056)	(40,234)		(16,393)	(40,234)
Net cash used in investment activities	(15,776,978)	(9,966,154)		(15,703,622)	(9,975,642)

Cash flows from financing activities
Borrowings and financing
Funding	18,462,151	6,870,754		18,336,072	6,870,754
Amortization	(4,295,849)	(2,246,263)		(4,295,849)	(2,246,263)
Payment of interest on capital	(2,363,776)	(928,851)		(2,363,776)	(928,851)
Public-Private Partnership - PPP	(480,492)	(569,725)		(480,492)	(569,725)
Program Contract Commitments	-	(35,497)		-	(35,497)
Derivative financial instruments - Paid/received	(397,443)	324,778		(397,443)	324,778
Treasury shares	(475,385)	-		(475,385)	-
Net cash generated from (used in) financing activities	10,449,206	3,415,196		10,323,127	3,415,196

Increase / (decrease) in cash and cash equivalents in the year	2,888,794	842,866		2,980,620	844,122

Represented by:
Cash and cash equivalents at the beginning of the year	1,681,204	838,338		1,682,606	838,484
Cash and cash equivalents at the end of the year	4,569,998	1,681,204		4,663,226	1,682,606
Increase / (decrease) in cash and cash equivalents in the year	2,888,794	842,866		2,980,620	844,122

The accompanying notes are an integral part of these financial statements.


	F-20

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Statements of Value Added for the

Years ended December 31, 2025 and 2024

In thousands of reais (continued)

		Individual		Consolidated
	Note	2025	2024	2025	2024
Revenue
Sanitation services (includes FAUSP)	30	23,757,444	23,464,821	23,794,887	23,499,676
Financial asset of the concession		1,676,434	9,151,310	1,676,434	9,151,310
Construction	30	14,430,593	6,220,581	14,437,363	6,225,871
Other revenue		505,354	64,587	505,354	64,587
Allowance for doubtful accounts	10 (c)	(61,450)	(557,126)	(62,067)	(557,789)
		40,308,375	38,344,173	40,351,971	38,383,655
Inputs purchased from third parties
Operating and construction costs		(18,391,956)	(10,255,112)	(18,405,676)	(10,272,227)
Materials, electricity, outsourced services, and others		(770,886)	(2,251,999)	(785,461)	(2,254,677)
Other operating expenses	33	(220,234)	(339,513)	(220,234)	(339,513)
		(19,383,076)	(12,846,624)	(19,411,371)	(12,866,417)

Gross value added		20,925,299	25,497,549	20,940,600	25,517,238

Retentions
Depreciation and amortization	31	(2,203,829)	(2,671,709)	(2,208,762)	(2,676,642)

Wealth created by the Company		18,721,470	22,825,840	18,731,838	22,840,596

Wealth received in transfer
Equity Accounting	12	48,644	21,622	48,153	35,322
Financial income		3,618,328	1,126,426	3,619,978	1,114,115
		3,666,972	1,148,048	3,668,131	1,149,437

Total value added to distribute		22,388,442	23,973,888	22,399,969	23,990,033

Value added distribution

Personnel
Direct Compensation		1,658,383	2,543,481	1,659,440	2,545,043
Benefits		945,497	640,138	945,497	640,138
Guarantee Fund for Length of Service (FGTS)		300,171	195,077	300,171	195,077
		2,904,051	3,378,696	2,905,108	3,380,258
Taxes, fees, and contributions
Federal		5,547,432	7,272,178	5,553,026	7,279,817
State		198,158	174,544	203,867	174,721
Municipal		81,771	68,759	81,771	68,775
		5,827,361	7,515,481	5,838,664	7,523,313
Value distributed to providers of capital
Interest, exchange rate changes and inflation adjustments		5,170,715	3,469,401	5,169,882	3,476,152
Rentals		24,256	30,747	24,256	30,747
		5,194,971	3,500,148	5,194,138	3,506,899
Value distributed to shareholders
Interest on Equity		2,381,562	1,831,122	2,381,562	1,831,122
Dividend distribution		-	718,692	-	718,692
Retained earnings		6,080,497	7,029,749	6,080,497	7,029,749
		8,462,059	9,579,563	8,462,059	9,579,563

Value added distributed		22,388,442	23,973,888	22,399,969	23,990,033

The accompanying notes are an integral part of these financial statements.


	F-21

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

1	Operations

Companhia de Saneamento Básico do Estado de São Paulo (“SABESP” or “Company”) is a publicly-held company headquartered in the municipality of São Paulo, at Rua Costa Carvalho, 300, CEP 05429-900. The Company is engaged in the provision of basic and environmental sanitation services in São Paulo State, and supplies treated water and sewage services on a wholesale basis. SABESP may perform activities in other states and countries and can operate in drainage, urban cleaning, solid waste handling, and energy markets.

The Company's shares have been listed on the Novo Mercado segment of B3 under ticker SBSP3 since April 2002 and on the New York Stock Exchange (“NYSE”) as Level III American Depositary Receipts (“ADRs”), under ticker SBS, since May 2002.

Approvals

The financial statements were approved by the Board of Directors on March 16, 2026.

2	Basis of preparation and presentation of the financial statements

The Company's financial statements were prepared and are being presented in accordance with the International Financial Reporting Standards (IFRS), issued by the International Accounting Standards Board (IASB), and the accounting practices adopted in Brazil, which observe the pronouncements issued by the Brazilian Accounting Pronouncements Committee (CPC), and which were approved by the Brazilian Securities and Exchange Commission (“CVM”). All material information related to the financial statements, and this information alone, is being disclosed and corresponds to the information used by the Company’s Management in its administration.

The financial statements were prepared based on historical cost, except for certain financial instruments measured at their fair values when required by the standards.

The preparation of the financial statements, in compliance with IFRS and CPCs, requires the use of certain essential accounting estimates. In addition, it requires Management to exercise its judgment in the process of applying the Company's accounting policies. The areas that involve a greater degree of judgment or complexity or which assumptions and estimates are significant to the financial statements are described in Note 6.

The Company prepared the financial statements on a going concern basis.

The amounts disclosed in the Notes are presented in thousands of reais, unless otherwise stated.

3	Summary of material accounting policy information

The accounting practices are presented in the respective notes for a better understanding of the recognition and measurement basis applied in the preparation of the financial statements.

3.1

Consolidation

The consolidated financial statements comprise the financial statements of the Company and its subsidiaries as of December 31, 2025. The Company controls an entity when (i) it has power over the investee; (ii) it is exposed or is


	F-22

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

entitled to the variable returns arising from its involvement with the investee; and (iii) it has the ability to use this power to influence its returns.

When the Company does not hold the majority of the voting rights in an investee, it will have power over the investee when the voting rights are sufficient to effectively enable it to conduct the relevant activities of the investee unilaterally.

The financial statements of the subsidiary are included in the consolidated financial statements from the date on which the Company obtains control until the date on which this control ceases to exist. The revenues and expenses of a subsidiary acquired or disposed of during the year are included in the income statement from the date on which the Company obtains control until the date on which the Company ceases to control the subsidiary.

The consolidated financial statements were prepared for the same reporting date of the individual financial statements.

All intra-group balances, revenues and expenses and unrealized gains and losses arising from intra-group transactions were eliminated. The other comprehensive income of the subsidiaries, when applicable, will be recorded directly in the Company's equity under "other comprehensive income".

In the individual financial statements, the investments of the Company in its subsidiaries are accounted for based on the equity accounting method.

For details of the consolidation basis, as well as the Company's percentage interest in its subsidiaries, see Note 12.

3.2

Statement of Value Added (SVA)

This statement is intended to show the wealth generated by the Company and its distribution during a given period and is presented as required by accounting practices adopted in Brazil, as supplementary information to the financial statements for IFRS purposes.

The DVA was prepared based on information obtained from the accounting records that support the preparation of the financial statements. The first part presents the wealth created by the Company represented by revenue, inputs purchased from third parties and retentions, as well as the wealth received in transfer, represented by equity accounting and financial income. The second part presents the value added distribution among personnel, taxes, fees and contributions, value distributed to providers of capital and value distributed to shareholders.

3.3

Foreign currency balance translation

(a)

Functional currency and presentation currency

Items included in the financial statements are measured using the currency of the primary economic environment in which the entity operates (“functional currency”). The functional currency of the parent company and the presentation currency of the Company's individual and consolidated financial statements is the Brazilian real. Each group entity determines its own functional currency, and in those whose functional currencies are different from the real, the financial statements are translated into the real on the reporting date.


	F-23

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

(b)

Foreign currency translation

Transactions in foreign currency are initially recorded at the exchange rate of the functional currency in effect at the date of the transaction. Monetary assets and liabilities denominated in foreign currency are translated using the closing exchange rate at the reporting date.

Foreign exchange gains and losses resulting from the settlement of these transactions and the translation of monetary assets and liabilities denominated in foreign currency are recognized in the income statement, except for borrowings and financing that are related to property, plant and equipment or intangible assets in progress, and foreign exchange losses are recognized against the asset itself while it is in progress, as described in the accounting policy of Note 17.

4	Changes in accounting practices and disclosures

4.1

New standards, amendments and interpretations of standards that became effective for periods beginning on or after January 1, 2025

The amendments to CPC 02 (R2) / IAS 21 – The Effects of Changes in Foreign Exchange Rates; CPC 37 (R1) / IFRS 1 – First-time Adoption of International Financial Reporting Standards; CPC 18 (R3) / IAS 28 – Investments in Associates, Subsidiaries and Joint Ventures; ICPC 09 – Separate Financial Statements, Consolidated Financial Statements and Application of the Equity Method; and OCPC 10 – Carbon Credits (tCO2e), Emission Allowances, and Decarbonization Credits (CBIO), did not have any impact on the disclosures or amounts recognized in the annual financial statements.

4.2

New standards, amendments and interpretations of standards that are not yet effective

The Company has not adopted in advance and is evaluating the impacts on the disclosures or amounts recognized in the financial statements related to the following new and revised IFRSs that management deems applicable to the Company:


	F-24

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

Standard

Description

Impact

Amendments to CPC 48 / IFRS 9 – Financial Instruments and CPC 40 (R1) / IFRS 7 – Financial Instruments: Disclosures¹

Derecognition of financial liability settled by electronic transfer: the amendments allow the Company to consider as settled a financial obligation (or part of the financial obligation) that will be settled through an electronic payment system before the settlement date, if specific criteria are met. If an entity chooses to apply this accounting policy, it will be required to apply it to all settlements made through the same electronic payment system.

Contractual terms that are consistent with a basic lending agreement: the amendments provide guidance on how to assess whether the contractual cash flows of a financial asset are consistent with a basic lending agreement.

Financial assets with “non-recourse” characteristics: the amendments improve the description of the term “non-recourse”, in particular to specify that a financial asset has this characteristic when the entity's final right to receive cash flows is contractually limited to the cash flows generated by specific assets.

Contractually linked instruments: the amendments clarify the characteristics of contractually linked instruments that differentiate them from other transactions, highlighting that these instruments establish an order of priority in payments to holders of financial assets through multiple linked instruments, using a waterfall payment structure.

Investment in equity instrument designated at fair value through other comprehensive income: The requirements of CPC 40 / IFRS 7 were amended to require the disclosure of the fair value gain or loss recognized in comprehensive income during the period, separately disclosing the fair value gain or loss related to investments written off in the period and the fair value gain or loss related to investments held at the end of the period.

Contractual terms that may change the timing or amount of the contractual cash flows: the amendments require the disclosure of the contractual terms that may change the timing or amount of the contractual cash flows in the occurrence (or non-occurrence) of a contingent event that is not directly related to changes in the basic borrowing risks and costs. The requirements apply to each class of financial asset measured at amortized cost or at fair value through other comprehensive income, as well as to each class of financial liability measured at amortized cost.

The Company does not expect any effects arising from this Standard.


	F-25

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

Standard	Description	Impact

CPC 51 / IFRS 18 – Presentation and Disclosure in Financial Statements²	CPC 51 / IFRS 18 replaces CPC 26 (R1) / IAS 1 – Presentation of Financial Statements, transferring several of the unaltered requirements of CPC 26 (R1) and supplementing them with the new requirements. In addition, some paragraphs of CPC 26 (R1) were moved to CPC 23 / IAS 8 - IAS 8 – Accounting Policies, Changes in Accounting Estimates and Errors and CPC 40 (R1) / IFRS 7 – Financial Instruments: Disclosures. IASB also implemented minor changes to CPC 03 (R2) / IAS 7 – Statement of Cash Flows and CPC 41 / IAS 33 – Earnings per Share.	The Company is evaluating the impacts and effects of adopting this Standard.
IFRS 19 – Subsidiaries without Public Accountability: disclosures²	IFRS 19 allows an eligible subsidiary to provide reduced disclosures when applying Accounting Standards in the financial statements. The subsidiary is eligible for reduced disclosures if it has no public accountability and its ultimate or any intermediate controlling entity prepares consolidated financial statements available to the public meeting the Accounting Standards. IFRS 19 is optional for eligible subsidiaries and describes the disclosure requirements for subsidiaries that choose to apply it.	The Company does not expect any effects arising from this Standard.

Effective for annual periods beginning on or after January 1, 2026.

Effective for annual periods beginning on or after January 1, 2027.

There are no other standards and interpretations issued and not yet adopted that may, in the Management’s opinion, have a significant impact on the profit or loss for the year or on the equity disclosed by the Company in its financial statements.

5	Risk management

5.1

Financial risk management

Financial risk factors

The Company's activities are affected by the Brazilian economic scenario, making it exposed to market risk (exchange rate and interest rate), credit risk, and liquidity risk. Financial risk management focuses on the unpredictability of financial markets and seeks to minimize potential adverse effects on financial performance. There were no changes in risk measurement policies, processes, and methods compared to the previous year.

(a)

Market risk

Foreign currency risk

It is the risk that the fair value of the future cash flows of a financial instrument will fluctuate due to variations in exchange rates. The Company's exposure to the risk of changes in exchange rates refers mainly to its financing activities, since the Company has foreign currency-denominated liabilities arising from long-term financing, in development institutions, at more attractive interest rates in US Dollar, Euro and Yen.

The management of currency exposure considers several current and projected economic factors, besides market conditions.


	F-26

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

This risk arises from the possibility that the Company may incur losses due to exchange rate fluctuations that would impact liability balances of foreign currency-denominated borrowings and financing and related finance costs. The Company manages its foreign exchange risk through hedging transactions since 2024 and negotiates the terms of the derivatives in order to comply with the terms of the exposure hedged under Note 19.

Part of the financial debt in the amount of R$ 10,632,252 as of December 31, 2025 (R$ 3,356,365 as of December 31, 2024), is indexed to the U.S. dollar, Euro and Yen. The exposure to currency risk is as follows:

	Individual		Consolidated		Individual and Consolidated
	December 31, 2025		December 31, 2025		December 31, 2024
	Foreign currency (in thousands)	R$	Foreign currency (in thousands)	R$	Foreign currency (in thousands)	R$
Borrowings and financing – US$	750,889	4,131,691	1,250,889	6,882,891	303,978	1,882,323
Borrowings and financing – Yen	62,496,777	2,196,137	62,496,777	2,196,137	36,787,581	1,452,006
Borrowings and financing – EURO	220,000	1,423,224	220,000	1,423,224	-	-
Interest and charges from borrowings and financing – US$		44,876		110,009		24,030
Interest and charges from borrowings and financing – Yen		8,818		8,818		8,364
Interest and charges from borrowings and financing – EURO		12,033		12,033		-
Fair value adjustment - US$		47,666		143,636		-
Fair value adjustment - Yen		(67,281)		(67,281)		34,388
Fair value adjustment - EURO		34,631		34,631
Total Exposure		7,831,795		10,744,098		3,401,111
Borrowing cost – US$		(61,401)		(80,063)		(42,510)
Borrowing cost – Yen		(12,389)		(12,389)		(2,236)
Borrowing costs – EURO		(19,394)		(19,394)		-
Total foreign currency-denominated borrowings (Note 17)		7,738,611		10,632,252		3,356,365

The table below shows the prices and exchange rate changes in the period:

	December 31, 2025	December 31, 2024	Variation
US$	R$ 5.5024	R$ 6.1923	-11.14%
EURO	R$ 6.4692	R$ 6.4363	0.51%
Yen	R$ 0.03514	R$ 0.03947	-10.97%

As of December 31, 2025, if the Brazilian real had depreciated or appreciated by 10 percentage points, against the U.S. dollar, Yen and Euro with all other variables held constant, the effects on profit or loss before borrowing costs and taxes, for the year ended December 31, 2025 would have been R$ 1,063,311 (R$ 336,672 for the year ended December 31, 2024), upwards or downwards, excluding the effects of to the hedging instruments (Note 19).

The Company understands that it could comfortably accommodate any devaluation scenario due to derivative financial instruments such as cross-currency swaps already contracted.

Interest rate risk

It is the risk that the fair value of the future cash flows of a financial instrument will fluctuate due to variations in market interest rates. For most transactions, the Company manages the interest rate risk by entering into derivative financial instruments that effectively swap their exposures for liabilities indexed to the CDI.

The table below shows the borrowings and financing subject to different inflation adjustment indices, including the derivative instrument:


	F-27

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Individual		Consolidated
	December 31, 2025	*December 31, 2024 ()**	December 31, 2025	*December 31, 2024 ()**
CDI (i)	33,593,125	15,250,135	30,722,218	15,250,135
TR (ii)	1,629,756	1,683,342	1,629,756	1,683,342
IPCA (iii)	2,924,904	2,982,735	5,582,893	2,982,735
TJLP (iv)	825,206	1,067,436	825,206	1,067,436
SOFR (v)	-	1,882,325	-	1,882,325
Interest and charges	1,204,818	572,399	1,164,744	572,399
Total	40,177,809	23,438,372	39,924,817	23,438,372

(i)	CDI - (Certificado de Depósito Interbancário), an interbank deposit certificate
(ii)	TR - Benchmark Interest Rate
(iii)	IPCA - (Índice Nacional de Preços ao Consumidor Amplo), a consumer price index
(iv)	TJLP - (Taxa de Juros a Longo Prazo), a long-term interest rate index
(v)	SOFR - Secured Overnight Financing Rate
(*)	As of December 31, 2024, the amounts excluded the derivative instrument for comparative purposes.

Another risk to which the Company is exposed is the mismatch of inflation adjustment indices of its debts with those of its service revenues and financial assets, adjusted by the IPCA. Tariff adjustments of services provided do not necessarily follow the increases in the adjustments indices of borrowings, financing, and interest rates affecting indebtedness.

As of December 31, 2025, if interest rates on borrowings and financing had been 1 percentage point higher or lower with all other variables held constant, the effects on consolidated profit before taxes for the year ended December 31, 2025 would have been R$ 339,248 (R$ 234,384 for the year ended December 31, 2024), upwards or downwards, mainly as a result of lower or higher interest expenses on floating rate borrowings and financing.

The table below shows the sensitivity analysis of the financial instruments, prepared under CPC 40 (R1)/ IFRS 7, to evidence the balances of main financial assets and liabilities, calculated at a rate projected for the twelve-month period after December 31, 2025, or until the final settlement of each contract, whichever occurs first, considering a probable scenario.

The purpose of the sensitivity analysis is to measure the impact of changes in the market on the financial instruments, considering all other variables constant. At the time of settlement, the amounts may be different from those presented, due to the estimates used in the measurement.

The table below considers the impact of the derivative instrument:

Individual			Consolidated
December 31, 2025			December 31, 2025
Indicators	Exposure	Probable scenario	Exposure	Probable scenario

Assets
CDI	12,261,445	13.82%	12,261,445	13.82%
Financial income		1,694,532		1,694,532

Liabilities
CDI	(33,593,125)	13.82%	(30,722,218)	13.82%
Interest to be incurred		(4,642,570)		(4,245,811)
Net exposure – CDI	(21,331,680)	(2,948,038)	(18,460,773)	(2,551,279)

Assets
IPCA	21,665,330	3.99%	21,665,330	3.99%
Financial asset of the concession		864,858		864,858

Liabilities
IPCA	(2,924,904)	3.99%	(5,582,893)	3.99%
Interest to be incurred		(116,759)		(222,864)
Net exposure – IPCA	18,740,426	748,099	16,082,437	641,995

Liabilities
TR	(1,629,756)	0.0204%	(1,629,756)	0.0204%
Expenses to be incurred		(332)		(332)

TJLP	(825,206)	9.22%	(825,206)	9.22%
Interest to be incurred		(76,123)		(76,123)

Total net expenses to be incurred		(2,276,394)		(1,985,739)


	F-28

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

(b)

Credit risk

Credit risk is related to cash and cash equivalents, financial investments, as well as credit exposures of customers, including accounts receivable, restricted cash, accounts receivable from related parties, and financial asset of the concession. Credit risk exposure to customers is mitigated by sales to a dispersed base, without risk of concentration, while credit risk exposure to cash and investment is mitigated by the Financial Investment Guideline followed by the Company.

The maximum exposure to credit risk as of December 31, 2025, is the carrying amount of instruments classified as cash and cash equivalents, financial investments, restricted cash, trade receivables, accounts receivable from related parties, and financial asset of the concession at the reporting date. See Notes 7, 8, 9, 10 and 11.

Regarding the financial assets held with financial institutions, the credit quality was assessed by reference to external credit ratings (if available) or historical information about the bank’s default rates. For the credit quality of the banks, such as deposits and financial investments, the Company assesses the rating published by three main international agencies (Fitch, Moody's and S&P).

As of December 31, 2025, all investments were made with financial institutions whose rating disclosed by Fitch or Moody's was AAA (bra) or AAA.br.

(c)

Liquidity risk

Liquidity is primarily reliant upon cash provided by operating activities and borrowings and financing obtained in the local and international capital markets, as well as the payment of debts. The management of this risk considers the assessment of its liquidity requirements to ensure it has sufficient cash to meet its operating and capital expenditure requirements.

The funds held are invested in interest-bearing current accounts, time deposits, and securities, with instruments with appropriate maturity or liquidity to provide margin as determined by the projections mentioned above.

The table below shows the financial liabilities, by maturity, including the installments of principal and future interest. For agreements with floating interest rates, the interest rates used correspond to the base date of December 31, 2025.


	F-29

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Individual
	2026	2027	2028	2029	2030	2031 to 2048	Total
As of December 31, 2025
Liabilities
Borrowings and financing	5,132,890	2,259,452	1,794,449	4,172,569	7,299,157	19,643,086	40,301,603
Interest on borrowings and financing	3,497,069	3,606,943	3,433,949	3,164,611	2,855,487	7,456,409	24,014,468
Trade payables and contractors	2,398,445	-	-	-	-	-	2,398,445
Services payable	2,767,899	-	-	-	-	-	2,767,899
Public-Private Partnership - PPP	239,065	239,066	239,066	239,066	239,066	2,130,366	3,325,695
Interest Public-Private Partnership - PPP	230,622	248,333	266,562	285,472	305,090	3,311,812	4,647,891
Total	14,265,990	6,353,794	5,734,026	7,861,718	10,698,800	32,541,673	77,456,001

	Consolidated
	2026	2027	2028	2029	2030	2031 to 2048	Total
As of December 31, 2025
Liabilities
Borrowings and financing	5,092,816	2,259,452	1,794,449	4,172,569	7,336,464	19,486,597	40,142,347
Interest on borrowings and financing	3,497,069	3,772,445	3,590,853	3,321,945	3,012,391	7,613,313	24,808,016
Trade payables and contractors	2,400,046	-	-	-	-	-	2,400,046
Services payable	2,772,416	-	-	-	-	-	2,772,416
Public-Private Partnership - PPP	239,065	239,066	239,066	239,066	239,066	2,130,366	3,325,695
Interest Public-Private Partnership - PPP	230,622	248,333	266,562	285,472	305,090	3,311,812	4,647,891
Total	14,232,034	6,519,296	5,890,930	8,019,052	10,893,011	32,542,088	78,096,411

Cross default

The Company has borrowings and financing agreements including cross-default clauses, i.e., the early maturity of any debt may imply the early maturity of these agreements. The indicators are continuously monitored to avoid the execution of these clauses, and the most restrictive ones are shown in Note 17 (c).

(d)

Derivative financial instruments

Under the Financial Risk Management Policy and the Derivatives Transactions Program, which aim to manage financial risks and mitigate exposure to market variables that impact assets, liabilities, and/or cash flows, the Company enters into hedging instruments, especially for its foreign-currency financing, reducing the effects of undesirable fluctuations from these variables on its transactions.

Criteria and guidelines for financial risk management were established to mitigate imbalances between assets and liabilities that have some sort of indexation exclusively to hedge the Company’s indexed assets and liabilities that present some mismatch, without characterizing financial leverage.

The Company uses risk ratings disclosed by Standard Poor’s (S&P), Moody’s, or Fitch to support and complement the analysis and judgment of banking risk.

5.2

Capital Management

The Company’s objectives in managing capital are to ensure the Company’s ability to continue increasing investments in infrastructure, provide returns for shareholders and benefits for other stakeholders, and maintain an optimal capital structure to reduce the cost of capital.

Capital is monitored based on the financial leverage ratio, which corresponds to net debt divided by total capital (shareholders and providers of capital). Net debt corresponds to total borrowings and financing less cash and cash


	F-30

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

equivalents and financial investments. Total capital is calculated as total equity plus net debt, as shown in the statement of financial position.

	Individual		Consolidated
	December 31, 2025	December 31, 2024	December 31, 2025	December 31, 2024

Total borrowings and financing (Note 17)	40,301,603	25,258,297	40,142,347	25,258,297
(-) Cash and cash equivalents (Note 7)	(4,569,998)	(1,681,204)	(4,663,226)	(1,682,606)
(-) Financial investments (Note 8)	(7,693,630)	(3,694,029)	(7,707,745)	(3,699,694)

Net debt	28,037,975	19,883,064	27,771,376	19,875,997
Total Equity	42,401,124	36,928,054	42,401,124	36,928,054

Total capital (shareholders plus providers of capital)	70,439,099	56,811,118	70,172,500	56,804,051

Total	40%	35%	40%	35%

6	Significant accounting estimates and judgments

The preparation of the financial statements requires Management to disclose judgments (except for those that involve estimates) that have a significant impact on the amounts recognized based on experience and other factors deemed as relevant, which affect the amounts of assets and liabilities and present results that may differ from the actual results.

The Company establishes estimates and assumptions concerning the future, which are reviewed on a timely basis. Such accounting estimates, by definition, may differ from the actual results. The effects arising from the reviews of the accounting estimates are recognized in the period in which the estimates are reviewed.

The areas that require a higher level of judgment and greater complexity are disclosed below. The assumptions and estimates for each of these areas, when applicable, are presented in the related notes:

Area	Reference
Unbilled revenue	Note 10
Allowance for doubtful accounts	Note 10 (c)
Contract assets, intangible assets and financial assets arising from concession contracts	Note 13
Assessment of the recoverable amount of non-financial assets (impairment)	Note 13, 14 and 16
Derivative financial instruments	Note 19
Deferred income tax and social contribution	Note 22
Provisions	Note 23
Pension obligations – Pension plans	Note 25

7	Cash and cash equivalents

	Individual		Consolidated
	December 31, 2025	December 31, 2024	December 31, 2025	December 31, 2024
Cash and banks	2,185	30,382	95,411	31,784
Cash equivalents	4,567,813	1,650,822	4,567,815	1,650,822
Total	4,569,998	1,681,204	4,663,226	1,682,606


	F-31

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

Cash and cash equivalents include cash, bank deposits, and high-liquidity short-term financial investments, mainly represented by daily liquidity CDBs, whose original maturities or intention of realization are of less than three months, which are convertible into a cash amount and subject to an insignificant risk of change in value. Of the total balance presented in this item as of December 31, 2025, approximately 99.9% refers to the amounts recorded in Banco Itaú and Banco Bradesco.

As of December 31, 2025, approximately R$ 1,361,348 of the total Cash and cash equivalents will be allocated to the payment of FAUSP, once all conditions are met. See Note 26 for further details.

As of December 31, 2025, the average yield of cash equivalents corresponded to 99.6% of the CDI (96.83% as of December 31, 2024)

Accounting practice

Cash and cash equivalents include cash on hand, bank deposits, bank overdrafts, and other highly liquid short-term investments, with maturities and Management's intent for use within three months or less.

8	Financial investments

(a)

Current

The Company has financial investments in CDB, with daily liquidity, which it does not intend to use in the next three months, as shown below:

	Individual		Consolidated
	December 31, 2025	December 31, 2024	December 31, 2025	December 31, 2024
Banco BV	169	298	169	298
Banco Bradesco	1,118,026	1,442,159	1,118,026	1,442,159
Banco Santander S/A	3,699,510	1,194,678	3,699,510	1,194,678
Banco BTG Pactual S/A	2,132,826	226,819	2,132,826	226,819
Banco do Brasil S/A	83,594	1,355	97,709	7,020
Brazilian Federal Savings Bank	30,206	828,720	30,206	828,720
XP Investimentos	215,002	-	215,002	-
Banco Citibank	414,297	-	414,297	-
Total	7,693,630	3,694,029	7,707,745	3,699,694

As of December 31, 2025, the average yield of the financial investments corresponded to 99.6% of the CDI (101% as of December 31, 2024).

(b)

Noncurrent

In 2025, the Company fully redeemed investments totaling R$ 769 million as of December 31, 2024.


	F-32

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

Accounting policy

The Company analyzes fluctuations in investment rates for certificates of deposit, along with information from regulatory bodies regarding the issuing financial institutions. The 12-month probabilities of default were based on historical data provided by credit rating agencies for each credit grade and were analyzed in terms of sensitivity based on current returns.

These deposits and financial investments are subject to an insignificant risk of changes in value.

9	Restricted cash

Restricted cash balances refer to amounts held by the Company as a result of contractual obligations and specific agreements. As of December 31, 2025 and 2024, restricted cash operations were R$ 9,575 and R$ 37,715, respectively.

The amounts recorded in 2024 were mainly related to the agreements signed with the São Paulo Municipal Government (PMSP) and with URAE-1, which provided for the deduction of a portion of the revenue destined to the Municipal Fund for Environmental Sanitation and Infrastructure (FMSAI) to cover any defaults by public agencies. These amounts were redeemed throughout 2025, especially between October and November, resulting in the elimination of the balances linked to the agreements with the PMSP.

10	Trade receivables

(a)

Statement of financial position details

	Individual		Consolidated
	December 31, 2025	December 31, 2024	December 31, 2025	December 31, 2024
Private sector:
General (i) and special customers (ii)	2,431,979	2,404,631	2,436,976	2,409,094
Agreements (iii)	343,747	659,778	343,747	659,778
	2,775,726	3,064,409	2,780,723	3,068,872
Governmental Entities:
Municipal	1,186,815	689,688	1,186,531	690,010
Federal	2,670	5,297	2,670	5,303
Agreements (iii)	274,508	370,823	274,508	370,823
	1,463,993	1,065,808	1,463,709	1,066,136
Wholesale customers – Municipal governments: (iv)
Mogi das Cruzes	9,149	4,744	9,149	4,744
São Caetano do Sul	26,884	11,773	26,884	11,773
São Caetano do Sul - Agreement	51,589	65,213	51,589	65,213
Total wholesale customers – Municipal governments	87,622	81,730	87,622	81,730

Unbilled supply (v)	1,155,475	1,252,012	1,157,382	1,253,826

Sub-total	5,482,816	5,463,959	5,489,436	5,470,564

Allowance for doubtful accounts	(817,443)	(1,248,209)	(817,443)	(1,248,209)
Total	4,665,373	4,215,750	4,671,993	4,222,355

Current	4,406,829	3,887,952	4,413,449	3,894,557
Noncurrent	258,544	327,798	258,544	327,798
Total	4,665,373	4,215,750	4,671,993	4,222,355


	F-33

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

(i)	General customers - residential and small and mid-sized companies;
(ii)	Special customers – large consumers, industrial and commercial customers, condominiums and special billing customers (fixed demand agreements, industrial waste, wells, among others);
(iii)	Agreements - installment payments of past-due receivables, plus inflation adjustment and interest, according to the agreements;
(iv)	Wholesale basis customers - municipal governments. This balance refers to the sale of treated water to municipalities, which are responsible for distributing to, billing, and charging end consumers.
(v)	Unbilled Supplies: represents revenue incurred, for which the service has been provided but has not yet billed by the end of each period, and is recognized as trade receivables based on monthly estimates.

(b)

The aging of trade receivables is as follows:

	Individual				Consolidated
	December 31, 2025	%	December 31, 2024	%	December 31, 2025	%	December 31, 2024	%
Current	2,960,281		2,975,756		2,963,070		2,979,496
Past-due:
Up to 30 days	747,338	25%	636,024	26%	748,559	30%	637,375	26%
From 31 to 60 days	308,672	9%	302,595	12%	309,579	12%	303,238	12%
From 61 to 90 days	228,767	6%	177,481	7%	229,559	9%	177,777	7%
From 91 to 120 days	242,688	6%	168,246	7%	243,256	10%	168,515	7%
From 121 to 180 days	276,103	10%	240,724	10%	276,446	11%	241,030	10%
From 181 to 360 days	226,600	4%	47,992	2%	226,600	9%	47,992	2%
Over 360 days	492,367	40%	915,141	37%	492,367	19%	915,141	37%
Total Past Due	2,522,535	100%	2,488,203	100%	2,526,366	100%	2,491,068	100%
Total	5,482,816		5,463,959		5,489,436		5,470,564

(c) Allowance for doubtful accounts (ADA)

	Individual and Consolidated
Changes in assets	2025	2024
Balance at the beginning of year	1,248,209	1,377,209
Recognition/(reversal) of allowance	(29,099)	41,793
Recoveries	(401,667)	(170,793)
Total	817,443	1,248,209


	F-34

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Individual		Consolidated
Reconciliation of estimated/historical losses in profit or loss	2025	2024		2025	2024

Write-offs	(501,169)	(684,918)		(501,786)	(685,581)
(Losses)/reversal with state entities - related parties	8,953	(1,208)		8,953	(1,208)
(Losses)/reversal with the private sector/government entities	29,099	(41,793)		29,099	(41,793)
Recoveries	401,667	170,793		401,667	170,793

Amount recorded as expense (Note 31)	(61,450)	(557,126)		(62,067)	(557,789)

The Company does not have customers individually accounting for 10% or more of its total revenues.

(d)

Registered warrants

The Company has registered warrants issued as a result of final and unappealable lawsuits for the collection of unpaid water and sewage bills from public entities. These bills are covered in full by ADA, and the restated amounts of said bills, calculated according to the respective registered warrants, are not recognized due to uncertainties about their realization.

Accordingly, the reversal of the ADA for the original bills and their restatement are recognized when uncertainties about their realization are mitigated, i.e. when the realizable value is determinable due to the predictability of the commencement of their receipt, without uncertainties or discussions about these amounts or when negotiated with third parties.

The Company had the following registered warrants issued on its behalf:

	Individual and Consolidated
Debtor	December 31, 2024	Discount (i)	Receipt (ii)	Assignment of Receivables (iii)	Others (iv)	December 31, 2025
Municipality of São Paulo	2,898,210	(992,289)	(1,217,593)	-	125,962	814,290
Municipality of Ferraz de Vasconcelos	22,883	(4,653)	(9,865)	(8,974)	609	-
Municipality of Cachoeira Paulista	12,608	(3,410)	(4,408)	(5,093)	303	-
Municipality of Agudos	14,039	(4,582)	(2,913)	(7,043)	499	-
Other	19,568	(13,727)	(3,587)	(5,382)	3,128	-
Total	2,967,308	(1,018,661)	(1,238,366)	(26,492)	130,501	814,290

(i)

Regarding the other two settlement proposals approved on April 9, 2025, in the restated amount of R$ 2.48 billion, by applying the discount rate according to the chronological order of payment, totaling R$ 1.52 billion (discount of R$ 960 million). In July 2025, the uncertainties and discussions surrounding this process ceased, and the Company recognized the effects of these registered warrants in the 3rd quarter and already received R$ 716,302 related to this settlement.

(ii)

Includes amounts received through lawsuits.

(iii)

In June 2025, the Company negotiated the assignment of receivables from various registered warrants.

(iv)

Mainly includes inflation adjustments.


	F-35

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

As of October 21, 2024, the Registered Warrants Conciliation Chamber of the Attorney General Office of the Municipality of São Paulo approved part of the agreement proposals submitted by SABESP for the settlement of registered warrant credits under the Notice for agreement 1/2024 and the Company received R$ 55,399 in February this year. In March, the Municipal Government of São Paulo raised objections to the calculations made by DEPRE/TJSP, contesting the income tax percentage used, both in the tax base and the applied rate. On July 15, 2025, the DEPRE/TJSP sent the Company an official letter approving the calculations and thus putting to an end any uncertainty and room for discussion around that proceeding. In view of the conclusion of the uncertainties and discussions surrounding this process, the Company recognized R$ 401,679 in the 3rd quarter of the current fiscal year and this amount was received in full.

Additionally, the Company negotiated registered warrants for overdue bills with the municipalities of Guarulhos, Santo André, and Mauá in previous fiscal years, which are currently suspended as they serve as collateral for the provision of services in these municipalities.

Accounting practice

Trade receivables correspond to amounts receivable for services provided in the ordinary course of activities. They are classified as current assets, except when the maturity is more than 12 months after the date of the statement of financial position, when they are classified as noncurrent.

Unbilled supply represents services provided to customers for which meter readings have not yet been made. They are recognized based on monthly estimates calculated according to the historical average billing of the respective account.

Due to the characteristics of the Company's accounts receivable, which have (i) an insignificant financial component; (ii) no complexity; and (iii) low credit risk, the simplified expected credit loss approach was adopted, which consists of recognizing the expected credit loss over the total useful life of the asset.

The Company recognizes the allowance for doubtful accounts in an amount considered sufficient by Management to cover probable losses, based on the analysis of trade receivables and in accordance with the accounting policy.

The methodology for estimating the allowance for doubtful accounts consisted of using an estimate calculated based on the average default observed in the last 36 months, by maturity range, in addition to estimating the recovery of overdue credits over 360 days, based on the history observed in the last 3 years. In addition, it considered for estimation purposes the category of private and public customers and segregated the accounts receivable between the normal consumption accounts and the agreements. The Company performed correlation analyses of the macroeconomic indicators Gross Domestic Product (GDP), Unemployment Rate and Extended National Consumer Price Index (IPCA) and its default history, and did not identify relevant impacts in the estimation of allowance for doubtful accounts.

The methodology to determine such losses requires significant estimates, considering a variety of factors, including the evaluation of the receipt history, current economic trends, maturity of the accounts receivable portfolio and expectations of future losses. Although the Company believes that the assumptions used are reasonable, the actual results may be different.


	F-36

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

11	Related-party balances and transactions

(a)

São Paulo State

(i)

Accounts receivable, interest on equity, revenue, expenses, and financial receipts

	Individual		Consolidated
	December 31, 2025	December 31, 2024	December 31, 2025	December 31, 2024

Current
Accounts receivable:
Sanitation services	163,759	173,434	163,865	173,466
Allowance for losses	(42,753)	(51,706)	(42,753)	(51,706)

Reimbursement of additional retirement and pension benefits paid (G0):
Monthly flow	32,141	84,973	32,141	84,973
GESP Agreement – 2015	123,135	112,813	123,135	112,813

Total current	276,282	319,514	276,388	319,546

Noncurrent
Agreement for the installment payment of sanitation services	1,361	1,361	1,361	1,361

Reimbursement of additional retirement and pension benefits paid (G0):
GESP Agreement – 2015	861,421	907,514	861,421	907,514

Total non-current	862,782	908,875	862,782	908,875

Total receivable	1,139,064	1,228,389	1,139,170	1,228,421

Assets:
Sanitation services	122,367	123,089	122,473	123,121
Reimbursement of additional retirement and pension benefits paid (G0)	1,016,697	1,105,300	1,016,697	1,105,300

Total	1,139,064	1,228,389	1,139,170	1,228,421

Liabilities:
Dividends and interest on capital payable	428,681	458,985	428,681	458,985

	Individual		Consolidated
	2025	2024	2025	2024

Revenue from sanitation services	952,461	891,101	952,803	891,312
Payments received from related parties	(910,676)	(843.026)	(910,676)	(843.026)

Reimbursement received referring to Law No. 4,819/1958	(276,307)	(178,941)	(276,307)	(178,941)

The information below refers to the Individual and Consolidated balances and transactions.

(ii)

Disputed amounts

As of December 31, 2025 and December 31, 2024, the disputed amounts receivable between SABESP and the São


	F-37

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

Paulo State, referring to additional retirement and pension benefits paid (Law No. 4,819/1958), totaled R$ 1,808,631 and R$ 1,685,493, respectively, and an ADA was recognized for the total amount, see Note 10 (c).

(iii)

Actuarial Liability

The Company recognized an actuarial liability corresponding to additional retirement and pension benefits paid to employees, retired employees, and pensioners of the G0, see Note 25. As of December 31, 2025 and December 31, 2024, the amounts corresponding to such actuarial liability were R$ 2,140,161 and R$ 1,931,145, respectively. For detailed information on additional retirement and pension benefits, see Note 25.

(iv)

Agreements with reduced tariffs for Federal, State and Municipal Entities that join the Rational Water Use Program (PURA)

The Company maintains joinder agreements to the PURE Program with public entities operating in the São Paulo State. The purpose of the program is to promote the conscious use of water, granting participating entities a 25% tariff discount, provided that they are in a regular situation of compliance and meet the established goals.

(v)

Guarantees

The São Paulo State provides guarantees for some of the Company’s borrowings and financing and does not charge any related fees, see Note 17.

(vi)

FEHIDRO

The Company formalized three financing agreements under the State Fund for Water Resources (FEHIDRO). The funds are aimed at the execution of works and sewage services. As of December 31, 2025, the balance of these financings was R$ 938, recorded under the “Other” line in borrowings and financing (R$ 2,799 as of December 31, 2024).

(b)

Non-operating assets

As of December 31, 2025, the Company had an amount of R$ 3,521 (R$ 3,613 as of December 31, 2024) related to land and lent structures under free lease agreements.

(c)

SABESPREV

The Company sponsors a defined benefit plan (G1 Plan), which is operated and administered by SABESPREV. The net actuarial commitment, recognized until December 31, 2025, was R$ 99,514. As of December 31, 2024, this plan had a surplus of R$ 132,244.

(d)

Key Management personnel compensation

The expenses related to the compensation of key management personnel were as follows:

Compensation		December 31, 2025
Short-term benefits to employees and key management personnel		39,828
Share-based payments		22,618
Total compensation		62,446


	F-38

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

(e)

Loan agreement through credit facility

Águas de Andradina

As of December 31, 2025, the balance of principal and interest was R$ 4,718, recorded under “Other assets” in current assets (R$ 4,007 in current assets as of December 31, 2024), at DI + 3% p.a.

This loan agreement was executed on August 17, 2021 and will be settled with the purchase and sale transaction. See further details in Note 12.

SABESP Olímpia

The Company signed a loan agreement with subsidiary Sabesp Olímpia S/A, making available the necessary funds for the payment of the Fixed Concession Fee to the Municipality, which was a prerequisite for the signing of the water and sewage concession agreement.

The loan agreement, of R$ 170,981, was used for capital increase in SABESP Olímpia in the first quarter of 2025, see Note 12.

(f)

Privatization

According to Article 7 of Law No. 9,361/1996, the controlling shareholder will be reimbursed, upon the privatization, the services of independent audit firms, law firms, opinions, or specialized studies necessary for the privatization.

The amount to be reimbursed by the São Paulo State as of December 31, 2025 was R$ 85,929, recorded under “Other assets” (R$ 99,653 as of December 31, 2024).

(g)

Equatorial S.A.

In July 2024, Equatorial Participações e Investimentos IV S.A., controlled by Equatorial S.A., acquired shares representing 15% (fifteen percent) of the share capital of SABESP. In December 2024, Equatorial S.A. absorbed its subsidiary, becoming the direct holder of the equity interest in SABESP. As of December 31, 2025, the balance of dividends and interest on equity payable was R$ 348,402 and (R$ 341,272 as of December 31, 2024).

(h)

SABESP Luxembourg (“SABESP Lux”)

On August 1, 2025, the Company issued the 36th issue of simple non-convertible unsecured debentures, in the total amount of 2,815,700, with a unit par value of R$ 1, with maturity in 2030 and a yield of IPCA + 9.28% p.a. (See Note 17 (a)). Of these debentures, 2,765,700 were acquired by SABESP Luxembourg (98.22% of the total securities of this issue). This transaction involved entering into a derivative instrument swapping the yield for CDI (see Note 19).

12	Investments

The following are events in the year that are related to investees:


	F-39

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

SABESP Participações S.A.

On August 19, 2025, SABESP Participações S.A. (“SABESPar”) was incorporated as a wholly-owned subsidiary of SABESP, with capital of R$ 1 in registered common shares without par value, fully subscribed and paid in. SABESPar was created for the purpose of acting as an investment and equity management vehicle, in line with SABESP's corporate strategy.

On November 3, 2025, SABESP carried out a capital increase in the amount of R$ 85,000, through the issuance of 85,000,000 new registered common shares with no par value.

SABESP Luxembourg (“SABESP Lux”)

As of May 8, 2025, SABESP Lux S.à r.l. (“SABESP Lux”) was incorporated in Luxembourg, which is fully controlled by SABESP, with capital of US$ 100 thousand. In this context, SABESP Lux will act as a strategic vehicle for raising funds in the international market, and for managing international financial assets and liabilities, contributing to the optimization of SABESP's capital structure.

As of July 17, 2025, SABESP, as the sole shareholder of SABESP Lux, carried out a capital increase of US$ 1,000 thousand. No new shares had to be issued for the capital increase that was recorded directly in the capital of SABESP Lux.

On October 15, 2025, SABESP carried out a capital increase in the amount of US$ 2,000 thousand. The capital increase was carried out without issuing new shares, being recorded directly in SABESP Lux's capital account.

Acquisition of investees Andradina and Castilho

As of May 28, 2025, SABESP entered into a Share Purchase and Sale Agreement and Other Covenants with Iguá Saneamento S.A. for the acquisition of common shares equivalent to 70% of the capital of each of the companies Águas de Andradina S.A. and Águas de Castilho S.A. that, added to the equity interests previously held by SABESP, totals 100% of the corporate capital of these companies.

In July 2025, the transaction was approved by the Brazilian Antitrust Agency (CADE); however, certain conditions precedent are still pending to this date.

The companies Andradina and Castilho have as their corporate purpose the provision of public water and sewage services and are the holders of concession contracts for the operation of the public water supply and sewage service in the municipalities of Andradina and Castilho, in the State of São Paulo. Both contracts are mature, with universalized services and jointly serve a population of approximately 82 thousand inhabitants.

Concessionária SABESP URAE-1 S.A

On October 29, 2025, Concessionária SABESP URAE-1 (“SABESP URAE”) was incorporated as a wholly-owned subsidiary of SABESP, with capital of R$ 1 in registered common shares without par value, fully subscribed and paid in. SABESPar was created for the purpose of acting as an investment vehicle, in line with SABESP's corporate strategy.

The Company holds equity interest valued under the equity method in the following investees:


	F-40

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Equity		Capital increase	Dividends	Profit (loss) for the Period			Equity Interest Percentage
	December 31, 2025	December 31, 2024	2025	2025	2025	*()**	2024	December 31, 2025	December 31, 2024

Sesamm	91,455	75,307	-	(5,382)	21,530	-	18,709	36%	36%
Águas de Andradina	41,291	37,959	-	(1,173)	4,505	-	4,939	30%	30%
Águas de Castilho	12,060	8,782	-	(892)	4,170	-	2,155	30%	30%
Attend Ambiental	60,961	55,162	-	(31,941)	37,740	-	18,886	45%	45%
Aquapolo Ambiental	143,988	116,688	-	(16,644)	43,944	-	41,004	49%	49%
Paulista Geradora de Energia	22,769	27,004	-	-	(1,107)	(3,128)	(443)	25%	25%
Cantareira SP Energia	10,975	10,613	-	-	362	-	(37)	49%	49%
Barueri Energia Renovável	252,212	251,420	-	-	(2,538)	3,330	(12,477)	20%	20%
Infranext	4,154	4,154	-	-	-	-	(522)	45%	45%
SABESP Luxembourg	8,452	-	17,054	-	(7,964)	(638)	-	100%	-
SABESP Participações	85,001	-	85,001	-	-	-	(13,700)	100%	100%
SABESP Olímpia	162,670	(16,766)	170,981	-	8,455	-	-	100%	-
Concessionária Sabesp URAE-1	1	-	1	-	-	-		100%	-

(*) The amount presented refers to the changes in the investee’s equity, since its financial statements for the year ended December 31, 2024, were disclosed after the publication of SABESP’s financial statements.

The balances of investments and the respective changes are as follows

	Individual
	Investments		Capital Contribution	Dividends	Reclassification ()**	Equity Accounting
	December 31, 2025	December 31, 2024	2025	2025	2025	2025	*()**	2024

Sesamm	32,924	27,111	-	(1,938)	-	7,751	-	6,735
Águas de Andradina	12,387	11,387	-	(352)	-	1,352	-	1,482
Águas de Castilho	3,618	2,635	-	(267)	-	1,250	-	647
Attend Ambiental	27,433	24,824	-	(14,374)	-	16,983	-	8,498
Aquapolo Ambiental	70,555	57,178	-	(8,155)	-	21,532	-	20,093
Paulista Geradora de Energia	5,693	6,750	-	-	-	(276)	(781)	(111)
Cantareira SP Energia	5,378	5,194	-	-	-	178	6	(18)
Barueri Energia Renovável	50,443	50,285	-	-	-	(508)	666	(2,612)
Infranext	-	-	-	-	-	-	-	608
SABESP Luxembourg	8,452	-	17,054	-	(638)	(7,964)	-	-
SABESP Participações	85,001	-	85,001	-	-	-	-	-
SABESP Olímpia	162,670	-	170,981	-	(16,766)	8,455	-	(13,700)

Total	464,554	185,364	273,036	(25,086)	(17,404)	48,753	(109)	21,622

Other investments	29,534	30,439

Total	494,088	215,803

(*) The amount presented refers to changes in the equity of the investee, as its financial statements for the year ended December 31, 2024 were issued after the disclosure of SABESP’s financial statements.

(**) The amount of the investee's loss in excess of the investment was reclassified to Noncurrent Liabilities.


	F-41

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Consolidated
	Investments		Dividends	Equity Accounting
	December 31, 2025	December 31, 2024	2025	2025	*()**	2024

Sesamm	32,924	27,111	(1,938)	7,751	-	6,735
Águas de Andradina	12,387	11,387	(352)	1,352	-	1,482
Águas de Castilho	3,618	2,635	(267)	1,250	-	647
Attend Ambiental	27,433	24,824	(14,374)	16,983	-	8,498
Aquapolo Ambiental	70,555	57,178	(8,155)	21,532	-	20,093
Paulista Geradora de Energia	5,693	6,750	-	(276)	(781)	(111)
Cantareira SP Energia	5,378	5,194	-	178	6	(18)
Barueri Energia Renovável	50,443	50,285	-	(508)	666	(2,612)
Infranext	-	-	-	-	-	608

Total	208,431	185,364	(25,086)	48,262	(109)	35,322

Other investments	45,927	30,439

Total	254,358	215,803

Accounting policy

The Company holds interests in certain Special Purpose Entities (“SPE”). Although SABESP has no majority shares of its investees, the shareholders’ agreement provides for the power of veto in certain management matters, however, it cannot use such power of veto in a way to affect the returns over the investments of these SPEs, which implies a mutually shared control (joint venture – CPC 19 (R2)/IFRS 11), except SABESP URAE, SABESP Participações, SABESP Olímpia and SABESP Luxembourg, in which the Company holds a stake of 100% and meets the control requirements, thus consolidating these companies. When assessing whether SABESP’s voting rights in an investee are sufficient to grant it power, the Company considers all relevant facts and circumstances, including: (i) the size of the Company’s voting rights relative to the size of the holdings of other voting-right holders; (ii) potential voting rights held by the Company, by other voting-right holders, or by other parties; (iii) rights arising from other contractual agreements; and (iv) any additional facts and circumstances that indicate whether the Company does or does not have the ability to direct the investee’s relevant activities.

13	Contract assets and other concession assets

	Individual
	December 31, 2024	Additions (i)	Write-offs	Transfers	Transfers of works to intangible assets (ii)	Transfers of works to financial asset of the concession (iv)	December 31, 2025 (iii)

Contract assets and other concession assets	4,872,410	16,677,794	(62,684)	24,108	(8,117,869)	(2,387,270)	11,006,489


	F-42

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Consolidated
	December 31, 2024	Additions (i)	Write-offs	Transfers	Transfers of works to intangible assets (ii)	Transfers of works to financial asset of the concession (iv)	December 31, 2025 (iii)

Contract assets and other concession assets	4,877,667	16,684,564	(62,684)	24,108	(8,117,869)	(2,387,270)	11,018,516

	Individual
	December 31, 2023	Additions	Write-offs	Transfers	Transfers of works to intangible assets	Transfers of works to financial asset of the concession (iv)	December 31, 2024

Contract assets and other concession assets	7,393,096	6,670,657	(164,022)	5,796	(7,455,330)	(1,577,787)	4,872,410

	Consolidated
	December 31, 2023	Additions	Write-offs	Transfers	Transfers of works to intangible assets	Transfers of works to financial asset of the concession (iv)	December 31, 2024

Contract assets and other concession assets	7,393,096	6,675,914	(164,022)	5,796	(7,455,330)	(1,577,787)	4,877,667

(i)

The Company considers in the contract asset’s additions other concession assets as shown in the table below:

Other concession assets	Individual	Consolidated
Advances	1,800,997	1,800,997
Software	389,438	389,438
Inventory	22,640	22,640
Others	34,126	34,126
Additions – Other concession assets	2,247,201	2,247,201
Additions / Revenue Construction (Note 30)	14,430,593	14,437,363
Total additions	16,677,794	16,684,564

Additionally, The largest additions in the period were located in the municipalities of São Paulo, Guarulhos, and Praia Grande, in the amounts of R$ 5,540 million, R$ 1,528 million and R$ 627 million, respectively.

(ii)

The largest transfers in the period were located in the municipalities of São Paulo, Guarulhos, and Praia Grande, in the amounts of R$ 3,490 million, R$ 1,182 million and R$ 429 million, respectively.

(iii)

The largest works were located in the municipalities of São Paulo, Guarulhos and Praia Grande, totaling R$ 3,215 million, R$ 764 million, and R$ 275 million, respectively.


	F-43

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

As of December 31, 2025 and December 31, 2024, the contract asset and other concession assets had no amounts recognized as right-of-use leases.

(a)

Capitalization of interest and other finance charges

The Company capitalizes interest, inflation adjustments, and exchange rate changes in contract assets and other concession assets during the construction period. From January to December 2025, the Company capitalized R$ 820,213 (R$ 564,302 from January to December 2024), as described in the accounting policy in Note 17.

(b)

Expropriations

As a result of the construction of priority projects related to water and sewage systems, the Company is required to expropriate third-party properties, whose owners are compensated either amicably or in court.

The costs of such expropriations are recorded in the contract asset during the execution of the works. From January to December 2025, the total amount referring to expropriations was R$ 55,545 (from January to December 2024 – R$ 64,047).

Accounting policy

The Contract Assets (works in progress) is the right to consideration in exchange for goods or services transferred to the customer. As determined by CPC 47/ IFRS 15 - Revenue from contracts with customers, the assets linked to the concession under construction, registered under the scope of ICPC 01 (R1) / IFRIC 12 - Concession Agreements, must be classified as Contract Assets during the construction period and transferred to Intangible Assets or Financial Assets on the Concession, after completion of the works.

The Company acts as the primary responsible party for the construction and installation of the infrastructure related to the concession, whether through its own efforts or by contracting third parties, being significantly exposed to its risks and benefits. Accordingly, until December 2024, the Company recognized construction revenue corresponding to construction costs plus a gross margin of 2.3%. As from January 1, 2025, the Company reassessed and concluded that the construction margin was zero.

Contract Assets and other concession assets are recognized at fair value, including interest and other financial charges capitalized during the construction period of the qualifying assets, when applicable, (except for advances, construction-in-progress inventories, and other assets) considering the weighted average rate of the loans in force on the capitalization date. Qualifying assets are those which necessarily requires a substantial period, established by the Company as greater than 12 months, to be ready for use, considering the period for completion of the works, since most of the works have an average period of more than 12 months, equivalent to one fiscal year of the Company.

The construction infrastructure amounts are recognized as revenue, at their fair value, provided that they generate future economic benefits. The accounting policy for recognition of construction revenue is described in Note 30.

The recognition of the fair value of intangible assets and financial assets, arising from the exchange of assets, involving concession agreements (bifurcation), is subject to assumptions and estimates, and the use of different estimates may affect the accounting records. In addition, the assessment of which expenses are capitalized in contract assets requires


	F-44

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

a certain level of judgment by Management. This fact, together with future changes in the useful life of these intangible assets, may have material impacts on the results of operations.

For further details regarding the capitalization of borrowing costs, see Note 17.

14	Intangible assets

(a)

Statement of financial position details

	Individual
	December 31, 2025			December 31, 2024
	Cost	Amortization	Net	Cost	Amortization	Net

Intangible assets arising from:
Concession agreements - others	135,470	(60,381)	75,089	112,456	(52,964)	59,492
Contract Commitments (i)	4,437,857	(707,736)	3,730,121	4,437,857	(588,098)	3,849,759
Concession Agreements - URAE-1	69,281,545	(23,335,074)	45,946,471	62,042,186	(22,085,992)	39,956,194
Software license of use	1,696,773	(1,145,671)	551,102	1,570,845	(932,558)	638,287
Right of use – other assets	240,646	(188,678)	51,968	240,106	(115,370)	124,736
Total	75,792,291	(25,437,540)	50,354,751	68,403,450	(23,774,982)	44,628,468

	Consolidated
	December 31, 2025			December 31, 2024
	Cost	Amortization	Net	Cost	Amortization	Net

Intangible assets arising from:
Concession agreements - new contracts	148,000	(10,275)	137,725	148,000	(5,344)	142,656
Concession agreements - others	135,470	(60,381)	75,089	112,456	(52,964)	59,492
Contract Commitments (i)	4,437,857	(707,736)	3,730,121	4,437,857	(588,098)	3,849,759
Concession Agreements - URAE-1	69,281,545	(23,335,074)	45,946,471	62,042,186	(22,085,992)	39,956,194
Software license of use	1,696,773	(1,145,671)	551,102	1,570,845	(932,558)	638,287
Right of use – other assets	240,646	(188,681)	51,965	240,106	(115,370)	124,736
Total	75,940,291	(25,447,818)	50,492,473	68,551,450	(23,780,326)	44,771,124

(i) With the enactment of the Basic Sanitation Law in 2007, contract renewals began to be executed through program agreements, under which the Company assumed assets and socio-environmental obligations and recognized them as intangible assets, which are amortized on a straight-line basis over the term of the agreements.

(b)

Changes

	Individual
	December 31, 2024	Additions	Transfer of contract asset	Transfers	Write-offs and disposals	Amortization	December 31, 2025

Intangible assets arising from:
Concession agreements – others	59,492	-	24,214	(1,627)	(3)	(6,987)	75,089
Contract Commitments	3,849,759	-	-	-	-	(119,638)	3,730,121
Concession Agreements URAE-1 (*)	39,956,194	2,666	7,990,514	(138,257)	(98,727)	(1,765,919)	45,946,471
Software license of use	638,287	-	103,141	-	-	(190,326)	551,102
Right of use – other assets	124,736	541	-	-	-	(73,309)	51,968
Total	44,628,468	3,207	8,117,869	(139,884)	(98,730)	(2,156,179)	50,354,751


	F-45

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Consolidated
	December 31, 2024	Additions	Transfer of contract asset	Transfers	Write-offs and disposals	Amortization	December 31, 2025

Intangible assets arising from:
Concession agreements – new contracts	142,656	-	-	-	-	(4,933)	137,723
Concession agreements – others	59,492	-	24,214	(1,627)	(4)	(6,987)	75,088
Contract Commitments	3,849,759	-	-	-	-	(119,638)	3,730,121
Concession Agreements URAE-1 (*)	39,956,194	2,666	7,990,514	(138,257)	(98,727)	(1,765,919)	45,946,471
Software license of use	638,287	-	103,141	-	-	(190,326)	551,102
Right of use – other assets	124,736	541	-	-	-	(73,309)	51,968
Total	44,771,124	3,207	8,117,869	(139,884)	(98,731)	(2,161,112)	50,492,473

(*) As of December 31, 2025, the line URAE-1 concession agreement included leases totaling R$ 154,449 (R$ 338,740 as of December 31, 2024). Also on this date, the accounting balance of intangible assets, contract assets and other concession assets, and financial assets of the concession aimed at URAE-1 amounted to R$ 79,924,407, accounting for 96.09% of the consolidated amount.

	Individual
	December 31, 2023	Additions	Transfer of contract asset	Transfers	Write-offs and disposals	Amortization	Transfer to Financial Assets	December 31, 2024

Intangible assets arising from:
Concession agreements – equity value (*)	506,117	-	13,216	(508,709)	(22)	(10,602)	-	-
Concession agreements – economic value	637,760	(181)	13,005	(576,439)	-	(74,145)	-	-
Concession agreements – others	-	-	4,090	57,445	-	(2,043)	-	59,492
Program contracts (*)	20,684,497	-	1,392,259	(21,469,330)	(1,020)	(606,406)	-	-
Program contracts – commitments	1,212,026	2,728,100	-	-	-	(90,367)	-	3,849,759
Service contracts – São Paulo	20,193,585	-	801,993	(20,278,339)	(1,327)	(715,912)	-	-
Concession Agreements URAE-1 (*)	-	20,712	6,573,841	42,727,540	(4,449)	(911,134)	(8,450,316)	39,956,194
Software license of use	513,224	29,972	234,713	4,989	-	(144,611)	-	638,287
Right of use – other assets	118,060	84,048	-	-	(46)	(77,326)	-	124,736
Total	43,865,269	2,862,651	9,033,117	(42,843)	(6,864)	(2,632,546)	(8,450,316)	44,628,468


	F-46

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Consolidated
	December 31, 2023	Additions	Transfer of contract asset	Transfers	Write-offs and disposals	Amortization	Transfer to Financial Assets	December 31, 2024

Intangible assets arising from:
Concession agreements – equity value	506,117	-	13,216	(508,709)	(22)	(10,602)	-	-
Concession agreements – economic value	637,760	(181)	13,005	(576,439)	-	(74,145)	-	-
Concession agreements – new contracts	147,589	-	-	-	-	(4,933)	-	142,656
Concession agreements – others	-	-	4,090	57,445	-	(2,043)	-	59,492
Program contracts	20,684,497	-	1,392,259	(21,469,330)	(1,020)	(606,406)	-	-
Program contracts – commitments	1,212,026	2,728,100	-	-	-	(90,367)	-	3,849,759
Service contracts – São Paulo	20,193,585	-	801,993	(20,278,339)	(1,327)	(715,912)	-	-
Concession Agreements URAE-1 (*)	-	20,712	6,573,841	42,727,540	(4,449)	(911,134)	(8,450,316)	39,956,194
Software license of use	513,224	29,972	234,713	4,989	-	(144,611)	-	638,287
Right of use – other assets	118,060	84,048	-	-	(46)	(77,326)	-	124,736
Total	44,012,858	2,862,651	9,033,117	(42,843)	(6,864)	(2,637,479)	(8,450,316)	44,771,124

(*) As of December 31, 2024, the lines Concession agreements – URAE-1 included leases totaling R$ 338,740 (R$ 374,679 as of December 31, 2023). Additionally, of the amount of transfers arising from the concession agreement, R$ 1,577,787 thousand relates to the transfer to the concession’s financial asset, as disclosed in Note 13.

(c)

Public-Private Partnership - PPP

SABESP carries out transactions related to the Public-Private Partnership. Such transactions, along with their corresponding guarantees and obligations, are supported by a contract established based on Law No. 11,079/2004.

The amounts recorded in intangible assets, item Concession agreements URAE-1, are shown in the table below:

	Individual and Consolidated
	December 31, 2025	December 31, 2024
Alto Tietê	202,823	219,096
São Lourenço	2,216,444	2,386,192

As of December 31, 2025 and December 31, 2024, the obligations assumed by the Company are as follows:

	Individual and Consolidated
	December 31, 2025			December 31, 2024
	Current Liabilities	Noncurrent Liabilities	Total liabilities	Current Liabilities	Noncurrent Liabilities	Total liabilities
São Lourenço	469,687	2,856,008	3,325,695	452,323	2,853,896	3,306,219

The chart below shows expenses with Public-Private Partnership from January to December 2025, compared to the figures reported in the same period in 2024:

	Individual and Consolidated
	December 31, 2025	December 31, 2024

General supplies	21,073	14,858
Outsourced services	44,466	31,351
General expenses	5,823	4,106
Amortization	169,659	127,373
Financial expenses	499,969	353,860
Total	740,990	531,548

In February 2024, the PPP Alto Tietê concluded its obligations. As of December 31, 2024, the line “Amortization” included the PPPs São Lourenço and Alto Tietê in the amounts of R$ 166,944 and R$ 2,715, respectively.


	F-47

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

As of December 31, 2025, the line “Amortization” referring to the PPP Alto Tietê included R$ 12,205.

(d)

Amortization of intangible assets

The average amortization rate was 2.6% and 2.8% as of December 31, 2025 and 2024, respectively.

(e)

Leases and right of use

	Individual and Consolidated
Nature	December 31, 2025	December 31, 2024

Leases - Concession Agreement URAE-1
Cost	405,245	588,534
Accumulated amortization	(250,796)	(249,794)
(=) Net	154,449	338,740

Right of use - Other assets
Vehicles	216,428	216,431
Properties	24,142	22,098
Equipment	76	1,577
Accumulated amortization	(188,678)	(115,370)
(=) Net	51,968	124,736

Total - Leases and Right of use	206,417	463,476

The lease liability corresponds to total future fixed lease payments, adjusted to present value, considering an incremental rate on borrowings. For further information, see Note 17.

The table below shows the impact on the Company’s profit or loss:

	Individual and Consolidated
	December 31, 2025	December 31, 2024

Right of use amortization	(108,596)	(114,111)
Financial result – interest expense and inflation adjustment	(156,251)	(134,509)
Expenses of short-term and low-value leases	(21,983)	(28,411)
Decrease in profit for the period	(286,830)	(277,031)

(f)

Performance Agreements

SABESP has contracts for the construction of assets under the performance-based model, in which the contractor is remunerated for the delivery of results and not merely for the execution of works. The accounting balances of current agreements recorded in the contract assets and other concession assets and intangible assets are as follows:


	F-48

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Individual and Consolidated
	December 31, 2025	December 31, 2024
Contract assets and other concession assets	601,064	380,204
Intangible assets	1,077,363	1,933,347
Total	1,678,427	2,313,551

As of December 31, 2025 and December 31, 2024, the obligations assumed by the Company are as follows:

	Individual and Consolidated
	December 31, 2025			December 31, 2024
	Current Liabilities	Noncurrent Liabilities	Total liabilities	Current Liabilities	Noncurrent Liabilities	Total liabilities

Performance Agreements	120,776	6,151	126,927	287,109	137,441	424,550

Accounting policy

The Company records as intangible assets those assets arising from concession agreements, which will be reversible to the granting authorities at the end of the concession term, and the main costs are transferred from the Contract Assets and other concession assets.

Amortization of the intangible asset begins when it becomes available for use, in the location and condition necessary for it to be capable of operating as intended, from the moment the asset goes into operation. Amortization reflects the period in which the future economic benefits of the asset are expected to be consumed by the Company, which may be the final term of the concession or its useful life.

Amortization of the intangible asset is terminated when the asset is fully consumed or written off, whichever occurs first.

Donations in assets received from third parties and government entities that allow the Company to provide water supply and basic sanitation services are recorded in the financial statements at zero cost, since these assets belong to the granting authority.

The financial resources received as donations for the construction of the infrastructure are recorded under “Other operating income”.

For the concession agreement with URAE-1 executed after the Company's privatization in July 2024, investments made and not amortized until the end of the concession are accounted for as Financial assets of the concession (Note 15).

Leases are recognized at the present value of contractual obligations, presented in assets as Right of Use (Note 14 (f)) and in liabilities as Leases (Note 17 (b)), except for short-term contracts (12 months or less) and/or low value (below US$ 5,000), which are recognized as expenses when incurred.


	F-49

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

(a)

Concession Agreements/URAE-1

The Company operates concession agreements including the provision of basic and environmental sanitation, water supply and sewage services, signed with the granting authorities. The infrastructure used by SABESP related to the service concession agreements is considered controlled by the granting authorities when:

(i)

The granting authority controls or regulates which services the provider must provide with the infrastructure, to whom it must provide and at what price; and

(ii)

The granting authority controls the infrastructure, i.e., it has the right to resume the infrastructure at the end of the concession.

The rights to the infrastructure operated in accordance with the concession agreements are accounted for as intangible assets, since the Company has the right to charge for the use of the infrastructure assets and users (consumers) have the obligation to pay for the services.

Intangible assets related to the concessions are amortized using the straight-line method according to the contract period or useful life of the underlying asset, whichever is the lower.

Details regarding the amortization of intangible assets are described in Note 14 (d).

(b)

Software licenses of use

Software licenses of use are capitalized based on acquisition costs and other implementation costs. Amortizations are recorded according to the useful life, and the expenses associated with their maintenance are recognized in profit or loss, when incurred.

Intangible assets are reviewed annually in order to identify evidence that may lead to losses of non-recoverable amounts, or whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. The Company does not have assets with indefinite useful lives and assessed that there is no indication of impairment loss, mainly supported by Law No. 14,026/2020, which ensures that public sanitation services will have economic and financial sustainability guaranteed, either through tariffs or indemnification.

15	Financial asset of the concession

With the completion of the privatization process and signing of the agreement with URAE-1 in July 2024, resulting in a single agreement covering 371 municipalities with a new expiration date in 2060, which provided greater legal security and granted an unconditional right to receive cash at the end of the concession, the Company recognized a modification in the agreement, leading to a bifurcation of concession assets considering the contractual right that reversible investments and not fully amortized by the end of the agreement must be compensated.

The impacts of Income and Social Contribution Taxes and PIS and Cofins are deferred until the time of their realization.

The change in the balance of the Financial Asset resulting from the concession agreement with URAE-1 is as follows:


	F-50

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

	Individual and Consolidated
	December 31, 2024	Transfer of contract asset (a)	Financial Asset of the Concession - Restatement (b)	December 31, 2025

Financial Asset of the Concession
Concession Agreement - URAE-1	17,601,626	2,387,270	1,676,434	21,665,330

(a) Correspond to transfers (bifurcation) of contract assets and other concession assets to the financial asset of the concession, which were previously recognized at their cost;

(b) Review of the financial asset considering the restatement using the IPCA, as this is the rate used by the regulatory agency for the adjustment of assets to be compensated.

Accounting policy

During the term of the concession agreements, SABESP makes continuous investments to ensure the quality and continuity of the services, and may replace the assets linked to the concession until the end of the agreement.

At the end of the concession, the infrastructure assets are reverted to the granting authority through indemnity when provided for in the agreement, calculated based on the fair value updated by the IPCA. SABESP recognizes the portion of investments in reversible assets not yet amortized at the end of the contract as a financial asset, recording its restatement as operating revenue, in line with the Company's business model. Accordingly, the Company treats the financial assets as a continuation of the contract asset related to the construction contract.

The restatement of the financial asset of the concession represents taxable income for PIS and Cofins purposes, subject to non-cumulative rates of 1.65% and 7.6%, respectively. However, given the relevance of the amounts involved, the Company carried out a formal consultation with the Regulatory Entity, in order to clarify what would be the most appropriate treatment to be given to this issue. ARSESP, in response to the consultation sent through Official Letter No. 180/2025-ARSESP-P, clarified that, effectively, the amounts related to taxes should be increased to the value of the investment classified as a financial asset.

As of December 2025, in line with ARSESP's definition of tax neutrality, Management reviewed the assumptions used in the recognition process of the financial asset.

This review aimed to more adequately reflect the amount to be unconditionally indemnified at the end of the concession term.

As a result of this review, there was a change in the accounting estimate related to the recognition of the amount of the financial asset corresponding to the increase in PIS and Cofins levied on the basis of the financial asset already recorded.

On December 31, 2025, the application of the new estimate resulted in the recognition of the additional amount of R$ 1 billion in financial assets, increasing, in the same amount, the operating revenue. Based on this amount, there is a deferred liability in the same proportion.


	F-51

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

The effects for subsequent periods will depend on the amounts actually recognized as a financial asset and its restatement, which can only be measured as they occur.

16	Property, plant, and equipment

(a)

Statement of financial position details

	Individual and Consolidated
	December 31, 2025				December 31, 2024
	Cost	Depreciation	Net	Useful Life	Cost	Depreciation	Net	Useful Life

Land	94,001	-	94,001	-	94,751	-	94,751	-
Buildings	134,818	(49,179)	85,639	50 years	127,968	(47,048)	80,920	50 years
Equipment	629,653	(346,037)	283,616	5 - 20 years	480,800	(331,056)	149,744	5 - 20 years
Transportation equipment	126,689	(18,394)	108,295	10 years	35,163	(11,624)	23,539	10 years
Furniture and fixtures	41,465	(19,141)	22,324	15 years	38,557	(17,777)	20,780	15 years
Power generation infrastructure	165,100	(18,084)	147,016	15 - 20 years	126,102	(4,569)	121,533	15 - 20 years
Other	7,278	(620)	6,658	20 years	7,487	(558)	6,929	20 years
Work in progress	143,242	-	143,242	-	63,352	-	63,352	-
Total	1,342,246	(451,455)	890,791		974,180	(412,632)	561,548

Changes

	Individual and Consolidated
	December 31, 2024	Additions	Transfers	Write-offs and disposals	Depreciation	December 31, 2025

Land	94.751	62	(812)	-	-	94.001
Buildings	80.920	1.173	5.682	-	(2.136)	85.639
Equipment	149.744	-	161.333	(563)	(26.898)	283.616
Transportation equipment	23.539	-	92.046	(5)	(7.285)	108.295
Furniture and fixtures	20.780	-	3.896	(93)	(2.259)	22.324
Power generation infrastructure	121.533	-	34.335	-	(8.852)	147.016
Other	6.929	-	(36)	(45)	(190)	6.658
Work in progress	63.352	290.755	(210.865)	-	-	143.242
Total	561.548	291.990	85.579	(706)	(47.620)	890.791

	Individual and Consolidated
	December 31, 2023	Additions	Transfers	Write-offs and disposals	Depreciation	December 31, 2024

Land	94.228	-	523	-	-	94.751
Buildings	73.088	670	9.404	-	(2.242)	80.920
Equipment	110.082	-	69.544	(256)	(29.626)	149.744
Transportation equipment	4.179	-	20.226	-	(866)	23.539
Furniture and fixtures	21.194	47	1.706	(31)	(2.136)	20.780
Power generation infrastructure	43.196	-	82.377	-	(4.040)	121.533
Other	6.873	12	249	-	(205)	6.929
Work in progress	121.720	99.998	(158.366)	-	-	63.352
Total	474.560	100.727	25.663	(287)	(39.115)	561.548


	F-52

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

Accounting policy

Property, plant, and equipment comprise, mainly, the administrative facilities that are not part of the assets object of the concession agreements and assets that are not reversible to the granting authority at the end of the concession. These assets are stated at acquisition or construction cost less depreciation and impairment losses, when necessary. When applicable, interest, other financial charges and inflationary effects arising from borrowings, effectively applied to fixed assets in progress, are computed as the cost of the respective fixed assets for qualifying assets. Qualifying assets are those which necessarily requires a substantial period, established by the Company as greater than 12 months, to be ready for use, considering the period for completion of the works, since most of the works have an average period of more than 12 months, equivalent to one fiscal year of the Company.

Subsequent costs are included in the carrying amount of the existing asset or recognized as a separate asset, as appropriate, only when it is probable that future economic benefits associated with the item will flow and that the cost of the item can be reliably measured. Repairs and maintenance are recorded in the profit or loss for the year, when incurred.

Depreciation of the property, plant, and equipment begins when the item becomes available for use, in the location and condition necessary for it to be capable of operating as intended, from the moment the asset goes into operation. Depreciation is calculated under the straight-line method and the average rates are presented in Note 16 (a). Land is not depreciated.

The useful lives of the assets are reviewed and restated, if applicable, at the end of each year.

Property, plant and equipment are reviewed annually in order to identify evidence that may lead to losses of non-recoverable amounts, or whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. The Company does not have assets with indefinite useful lives and assessed that there is no indication of impairment loss, mainly supported by Law No. 14,026/2020, which ensures that public sanitation services will have economic and financial sustainability guaranteed, either through tariffs or indemnification.

Gains and losses on disposals are determined by the difference between the sale value and the residual accounting balance and are recognized in profit or loss for the year, in other operating revenue (expenses).

The Company classifies non-current assets as held for sale when their carrying amount will be recovered, mainly, through a sale transaction instead of continuous use. These non-current and held-for-sale assets are measured at the lower of their carrying amount and the net fair value of selling expenses. Selling expenses are represented by incremental expenses directly attributable to the sale, excluding financial expenses and taxes on profit.

The classification criteria for non-current assets held for sale are met when the sale is highly probable and the asset or group of assets held for sale is available for immediate sale in its current condition, subject only to such terms as are customary for sale of such assets held for sale. The appropriate management level of the Company is committed to the asset sale plan, and a firm program has been initiated to locate a buyer and complete the plan within one year from the date of classification.

Property, plant and equipment and intangible assets are not depreciated or amortized when classified as held for sale.


	F-53

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

17	Borrowings and financing

Borrowings and financing outstanding balance	Individual
	December 31, 2025			December 31, 2024
Financial institution	Current	Noncurrent	Total	Current	Noncurrent	Total

Local currency
Debentures	2,764,582	20,230,117	22,994,699	1,323,040	10,373,183	11,696,223
Brazilian Federal Savings Bank	134,275	1,495,481	1,629,756	123,495	1,559,847	1,683,342
BNDES	259,341	564,501	823,842	262,709	803,011	1,065,720
IDB	307,349	2,680,484	2,987,833	260,899	3,425,530	3,686,429
IFC	64,450	2,645,882	2,710,332	44,200	2,706,779	2,750,979
Leases (Concession)	84,214	110,214	194,428	108,533	208,611	317,144
Leases (Other)	72,440	9,627	82,067	97,657	53,267	150,924
Other	616	328	944	1,868	931	2,799
Interest	1,139,091	-	1,139,091	548,372	-	548,372

Total in local currency	4,826,358	27,736,634	32,562,992	2,770,773	19,131,159	21,901,932

Foreign currency
IDB	56,573	973,833	1,030,406	89,222	919,189	1,008,411
IBRD	33,453	1,112,127	1,145,580	37,707	793,697	831,404
JICA	150,779	1,965,688	2,116,467	203,754	1,280,402	1,484,156
IFC	-	3,380,431	3,380,431	-	-	-
Interest	65,727	-	65,727	32,394	-	32,394

Total in foreign currency	306,532	7,432,079	7,738,611	363,077	2,993,288	3,356,365

Total borrowings and financing	5,132,890	35,168,713	40,301,603	3,133,850	22,124,447	25,258,297


	F-54

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

Borrowings and financing outstanding balance	Consolidated
	December 31, 2025			December 31, 2024
Financial institution	Current	Noncurrent	Total	Current	Noncurrent	Total

Local currency
Debentures	2,764,582	17,282,427	20,047,009	1,323,040	10,373,183	11,696,223
Brazilian Federal Savings Bank	134,275	1,495,481	1,629,756	123,495	1,559,847	1,683,342
BNDES	259,341	564,501	823,842	262,709	803,011	1,065,720
IDB	307,349	2,680,484	2,987,833	260,899	3,425,530	3,686,429
IFC	64,450	2,645,882	2,710,332	44,200	2,706,779	2,750,979
Leases (Concession)	84,214	110,214	194,428	108,533	208,611	317,144
Leases (Others)	72,440	9,627	82,067	97,657	53,267	150,924
Other	616	328	944	1,868	931	2,799
Interest	1,033,884	-	1,033,884	548,372	-	548,372

Total in local currency	4,721,151	24,788,944	29,510,095	2,770,773	19,131,159	21,901,932

Foreign currency
IDB	56,573	973,833	1,030,406	89,222	919,189	1,008,411
IBRD	33,453	1,112,127	1,145,580	37,707	793,697	831,404
JICA	150,779	1,965,688	2,116,467	203,754	1,280,402	1,484,156
IFC	-	3,380,431	3,380,431	-	-	-
Blue Bonds	-	2,828,508	2,828,508	-	-	-
Interest	130,860	-	130,860	32,394	-	32,394

Total in foreign currency	371,665	10,260,587	10,632,252	363,077	2,993,288	3,356,365

Total borrowings and financing	5,092,816	35,049,531	40,142,347	3,133,850	22,124,447	25,258,297


	F-55

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

(i) Payment schedule – accounting balances as of December 31, 2025

Payment Schedule	Individual
	2026	2027	2028	2029	2030	2031	2031 to 2048	Total

Local currency
Debentures	2,764,582	1,190,600	689,330	1,346,863	4,511,589	3,216,000	9,275,735	22,994,699
Brazilian Federal Savings Bank	134,275	142,638	151,387	157,420	155,126	141,077	747,833	1,629,756
BNDES	259,341	246,023	87,200	35,313	35,313	35,313	125,339	823,842
National IDBs	307,349	289,669	359,999	330,039	265,949	265,949	1,168,879	2,987,833
IFCs	64,450	91,400	147,450	218,700	335,000	559,800	1,293,532	2,710,332
Leases	156,654	7,950	17,778	23,696	12,549	52,327	5,541	276,495
Other	616	187	141	-	-	-	-	944
Interest and Other Charges	1,139,091	-	-	-	-	-	-	1,139,091
Total in local currency	4,826,358	1,968,467	1,453,285	2,112,031	5,315,526	4,270,466	12,616,859	32,562,992

Foreign currency
IDB	56,573	56,573	56,573	56,573	56,573	56,573	690,968	1,030,406
IBRD	33,453	33,453	33,453	78,294	78,294	78,294	810,339	1,145,580
JICA	150,779	200,959	251,139	251,139	174,232	174,232	913,987	2,116,467
IFCs	-	-	-	1,674,532	1,674,532	-	31,367	3,380,431
Interest and Other Charges	65,727	-	-	-	-	-	-	65,727
Total in foreign currency	306,532	290,985	341,165	2,060,538	1,983,631	309,099	2,446,661	7,738,611

Total	5,132,890	2,259,452	1,794,450	4,172,569	7,299,157	4,579,565	15,063,520	40,301,603


	F-56

Companhia de Saneamento Básico do Estado de São Paulo – SABESP

Notes to the Financial Statements for the

Years ended December 31, 2025 and 2024

In thousands of reais, unless otherwise stated

Payment Schedule

Consolidated

2026

2027

2028

2029

2030

2031

2031 to 2048

Filing Compare · COMPANHIA DE SANEAMENTO BASICO DO ESTADO DE SAO PAULO-SABESP