N-2 - $ / shares	6 Months Ended
N-2 - $ / shares	Mar. 31, 2025	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023
Cover [Abstract]
Entity Central Index Key	0001490349
Amendment Flag	false
Securities Act File Number	1-35040
Document Type	10-Q
Entity Registrant Name	PHENIXFIN CORPORATION
Entity Address, Address Line One	445 Park Avenue
Entity Address, Address Line Two	10th Floor
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10022
City Area Code	(212)
Local Phone Number	859-0390
Entity Emerging Growth Company	false
General Description of Registrant [Abstract]
Risk Factors [Table Text Block]	Item 1A. Risk Factors In addition to other information set forth in this report, you should carefully consider the “Risk Factors” discussed in our annual report on Form 10-K for the fiscal year ended September 30, 2024, filed with the SEC on December 17, 2024, which could materially affect our business, financial condition and/or operating results. Other than the items disclosed below, there have been no material changes during the six months ended March 31, 2025 to the risk factors discussed in “Item 1A. Risk Factors” of our annual report on Form 10-K. Additional risks or uncertainties not currently known to us or that we currently deem to be immaterial also may materially affect our business, financial condition and/or operating results. As of March 31, 2025, 16.1% of our total assets were invested in NSG, our insurance business. This significant exposure subjects our Company to various risks associated with such business (which are identified in “Risks of the Insurance Business” under Item 1A in our annual report on Form 10-K for the fiscal year ended September 30, 2024) to a much greater extent than companies not similarly concentrated.
NAV Per Share	$ 78.72	$ 79.37	$ 76.35	$ 70.75
Risks of the Insurance Business [Member]
General Description of Registrant [Abstract]
Risk [Text Block]	As of March 31, 2025, 16.1% of our total assets were invested in NSG, our insurance business. This significant exposure subjects our Company to various risks associated with such business (which are identified in “Risks of the Insurance Business” under Item 1A in our annual report on Form 10-K for the fiscal year ended September 30, 2024) to a much greater extent than companies not similarly concentrated.

PhenixFIN Corp 10-Q