UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of report (Date of earliest event reported): September 30, 2025

CLEARSIGN TECHNOLOGIES CORPORATION

(Exact name of registrant as specified in Charter)

Delaware		001-35521		26-2056298
(State or other jurisdiction of incorporation)		(Commission File No.)		(IRS Employee Identification No.)

8023 E. 63rd Place, Suite 101

Tulsa, Oklahoma 74133

(Address of Principal Executive Offices) (Zip Code)

(918) 236-6461

(Registrant's telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the Registrant under any of the following provisions (see General Instruction A.2 below).

¨	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR240.14a-12)

¨	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)).

¨	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13(e)-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock		CLIR		The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 3.01

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing.

As previously reported, on April 1, 2025, ClearSign Technologies Corporation (the “Company”), received a letter from the Listing Qualifications Staff of The Nasdaq Stock Market LLC (“Nasdaq”) indicating that the bid price for the Company’s common stock for the 30 consecutive business days beginning on February 18, 2025, and ending on March 31, 2025, had closed below the minimum $1 per share and, as a result, the Company was not in compliance with the $1 minimum bid price requirement for the continued listing on the Nasdaq Capital Market, as set forth in Nasdaq Listing Rule 5550(a)(2) (the “Bid Price Rule”).

On September 30, 2025, the Company received a second letter from Nasdaq granting the Company’s request for a 180-day extension to regain compliance with the Bid Price Rule. The Company now has until March 30, 2026, to meet the requirement. As part of the Company’s request for the 180-day extension, the Company notified Nasdaq that it intends to regain compliance with the Bid Price Rule by effecting a reverse stock split, if necessary. If at any time prior to March 30, 2026, the bid price of the Company’s common stock closes at $1 per share or more for a minimum of 10 consecutive business days, the Company will regain compliance with the Bid Price Rule.

If the Company does not regain compliance with the Bid Price Rule during the additional 180-day extension, Nasdaq will provide written notification to the Company that its common stock will be delisted. At that time, the Company may appeal the relevant delisting determination to a hearings panel pursuant to the procedures set forth in the applicable Nasdaq Listing Rules. However, there can be no assurance that, if the Company does appeal the delisting determination by Nasdaq to the hearings panel, that such appeal would be successful.

The Company will continue to monitor the closing bid price of its common stock and evaluate its available options to regain compliance with the Bid Price Rule. Nasdaq’s extension notice has no immediate effect on the listing or trading of the Company’s common stock, which continues to trade on the Nasdaq Capital Market under the ticker symbol “CLIR.”

Cautionary Statement Regarding Forward-Looking Statements

This Current Report on Form 8-K (this “Form 8-K”) contains “forward-looking statements” within the meaning established by the Private Securities Litigation Reform Act of 1995, which are identified by words such as “plans,” “will,” “expects,” “anticipates,” “may,” “believes,” “estimates” or “estimated, “intends,” and other similar words, expressions, and formulations. This Form 8-K contains forward-looking statements regarding the Company’s ability to regain compliance with the Bid Price Rule, the Company’s intentions to actively monitor the closing bid price of its common stock and the Company’s plans to consider implementing available options, including a reverse stock split, to regain compliance with the Bid Price Rule, and the Company’s intention to appeal any future delisting determination. The Company’s actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, including the risk that the Company may not meet the Bid Price Rule during any compliance period or in the future, the risk that the Company may not otherwise meet the requirements for continued listing under the Nasdaq Listing Rules, the risk that Nasdaq may not grant the Company relief from delisting if necessary, the risk that the Company may not ultimately meet applicable Nasdaq requirements if any such relief is necessary, the risk that the Company’s stockholders do not approve a reverse stock split, if needed, the risk that the Company is unable to timely effectuate a reverse stock split to regain compliance with the Bid Price Rule, among other risks and uncertainties. A detailed discussion of these and other risks and uncertainties that could cause the Company’s actual results to differ materially from these forward-looking statements is included in the documents that the Company files with the U.S. Securities and Exchange Commission, including its annual report on Form 10-K and quarterly reports on Form 10-Q. These forward-looking statements speak only as of the date of this Form 8-K, and the Company does not undertake any obligation to revise or update such statements, whether as a result of new information, future events, or otherwise.

Item 9.01

Financial Statements and Exhibits.

(d) Exhibits.

(d) Exhibits.

Exhibit No.		Description
104		Cover Page Interactive Data File (embedded within the Inline XBRL document).

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this Current Report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: September 30, 2025

	CLEARSIGN TECHNOLOGIES CORPORATION

	By:	/s/ Colin James Deller
	Name:	Colin James Deller
	Title:	Chief Executive Officer

ClearSign Technologies Corp 8-K