INVESTMENTS (Tables)

12 Months Ended

Sep. 30, 2025

Investments, Debt and Equity Securities [Abstract]

Schedule of Fair Value, Assets Measured on Recurring Basis

As of September 30, 2025 and 2024, our investments, by security type, at fair value were categorized as follows within the ASC 820 fair value hierarchy:

	Fair Value Measurements
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value
As of September 30, 2025:
Secured first lien debt	$	—	$	—	$	622,371	$	622,371
Secured second lien debt	—		—		150,542		150,542
Unsecured debt	—		—		333		333
Preferred equity	—		—		31,214		31,214
Common equity/equivalents	—		—		49,553		49,553
Total	$	—	$	—	$	854,013	$	854,013
Investments measured at NAV(A)	—		—		—		5,111
Total Investments	$	—	$	—	$	854,013	$	859,124
Cash Equivalents	31,774		—		—		31,774
Total Investments and Cash Equivalents as of September 30, 2025	$	31,774	$	—	$	854,013	$	890,898

	Fair Value Measurements
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value
As of September 30, 2024:
Secured first lien debt	$	—	$	—	$	554,937	$	554,937
Secured second lien debt	—		—		113,716		113,716
Unsecured debt	—		—		32		32
Preferred equity	—		—		31,346		31,346
Common equity/equivalents	—		—		96,191		96,191
Total	$	—	$	—	$	796,222	$	796,222
Investments measured at NAV(A)	—		—		—		38
Total Investments	$	—	$	—	$	796,222	$	796,260
Cash Equivalents	2,157		—		—		2,157
Total Investments and Cash Equivalents as of September 30, 2024	$	2,157	$	—	$	796,222	$	798,417

(A)Includes our investments in Gladstone Alternative and Leeds as of September 30, 2025 and our investment in Leeds as of September 30, 2024. Investments that are measured at fair value using NAV as a practical expedient have not been categorized in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented elsewhere in this annual report.

The following table presents our portfolio investments, valued using Level 3 inputs within the ASC 820 fair value hierarchy and carried at fair value as of September 30, 2025 and 2024 by caption on our accompanying Consolidated Statements of Assets and Liabilities, and by security type:

	Total Recurring Fair Value Measurements Reported in Consolidated Statements of Assets and Liabilities Using Significant Unobservable Inputs (Level 3)
	September 30, 2025			September 30, 2024
Non-Control/Non-Affiliate Investments
Secured first lien debt	$	517,762		$	540,661
Secured second lien debt	131,750			105,169
Unsecured debt	17			32
Preferred equity	16,794			27,247
Common equity/equivalents	29,958		(A)	77,757		(B)
Total Non-Control/Non-Affiliate Investments	$	696,281		$	750,866
Affiliate Investments
Secured first lien debt	$	34,713		$	380
Preferred equity	9,420			4,099
Common equity/equivalents	4,703			2,959
Total Affiliate Investments	$	48,836		$	7,438
Control Investments
Secured first lien debt	$	69,896		$	13,896
Secured second lien debt	18,792			8,547
Unsecured debt	316			—
Preferred equity	5,000			—
Common equity/equivalents	14,892			15,475
Total Control Investments	$	108,896		$	37,918
Total Investments at Fair Value Using Level 3 Inputs	$	854,013		$	796,222

(A)Excludes our investments in Gladstone Alternative and Leeds with fair values of $5.1 million and $36 thousand, respectively, as of September 30, 2025, which were valued using NAV as a practical expedient.

(B)Excludes our investment in Leeds with a fair value of $38 thousand as of September 30, 2024, which was valued using NAV as a practical expedient.

Schedule of Fair Value Measurement Inputs and Valuation Techniques

The table below is not intended to be all-inclusive, but rather provides information on the significant Level 3 inputs as they relate to our fair value measurements. The weighted average calculations in the table below are based on the principal balances for all debt related calculations and on the cost basis for all equity related calculations for the particular input.

	Quantitative Information about Level 3 Fair Value Measurements
							Range / Weighted Average as of
	September 30, 2025		September 30, 2024		Valuation Techniques/ Methodologies	Unobservable Input	September 30, 2025	September 30, 2024
Secured first lien debt	$	548,670	$	464,090	Yield Analysis	Discount Rate	9.4%–19.8% / 11.7%	10.8%–17.3% / 12.6%
	73,701		90,847		TEV	EBITDA multiple	3.5x–8.0x / 6.0x	4.1x–13.9x / 10.0x
						EBITDA	$538–$4,655 / $3,540	$3,020–$16,211 / $10,309
						Revenue multiple	0.6x–0.8x / 0.7x	0.2x–4.6x / 2.1x
						Revenue	$10,844–$21,649 / $15,090	$6,336–$21,118 / $13,981
Secured second lien debt	141,750		101,928		Yield Analysis	Discount Rate	11.4%–15.2% / 13.1%	12.2%—16.0% / 14.1%
	—		3,241		Market Quote	IBP	N/A	88.0%–88.0% / 88.0%
	8,792		8,547		TEV	EBITDA multiple	5.4x–5.4x / 5.4x	5.4x–5.4x / 5.4x
						EBITDA	$2,345–$2,345 / $2,345	$3,343–$3,343 / $3,343
Unsecured debt	333		32		TEV	EBITDA multiple	8.0x–8.0x / 8.0x	0.0x–0.0x / 0.0x
						EBITDA	$3,804–$3,804 / $3,804	$0–$0 / $0
						Revenue multiple	0.9x–0.9x / 0.9x	1.0x–1.0x / 1.0x
						Revenue	$4,846–$4,846 / $4,846	$7,834–$7,834 / $7,834
Preferred and common equity / equivalents(A)	80,767		127,537		TEV	EBITDA multiple	3.5x–14.6x / 6.8x	4.1x–13.9x / 8.0x
						EBITDA	$538–$142,549 / $10,222	$1,182–$144,458 / $10,847
						Revenue multiple	0.6x–0.9x / 0.7x	0.2x–4.6x / 2.0x
						Revenue	$4,846–$21,649 / $12,394	$4,672–$21,118 / $12,587
Total Level 3 Investments, at Fair Value	$	854,013	$	796,222

(A)Fair value as of September 30, 2025 includes one proprietary equity investment totaling $2.2 million, which was valued using the payoff amount as the unobservable input. Fair value as of September 30, 2025 excludes our investments in Gladstone Alternative and Leeds with fair values of $5.1 million and $36 thousand, respectively, which were valued using NAV as a practical expedient. Fair value as of September 30, 2024 excludes our investment in Leeds with a fair value of $38 thousand, which was valued using NAV as a practical expedient.

Schedule of Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation

The following tables provide the changes in fair value, broken out by security type, during the years ended September 30, 2025 and 2024 for all investments for which we determine fair value using unobservable (Level 3) inputs.

Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Year Ended September 30, 2025	Secured First Lien Debt		Secured Second Lien Debt		Unsecured Debt		Preferred Equity		Common Equity/ Equivalents		Total
Fair Value as of September 30, 2024	$	554,937	$	113,716	$	32	$	31,346	$	96,191	$	796,222
Total gains (losses):
Net realized gain (loss)(A)	(8,513)		—		—		(946)		64,827		55,368
Net unrealized appreciation (depreciation)(B)	(7,573)		285		(56)		6,510		7,179		6,345
Reversal of prior period net depreciation (appreciation) on realization(B)	9,612		295		—		946		(60,010)		(49,157)
New investments, repayments and settlements:(C)
Issuances/originations	322,603		57,958		357		12,762		3,026		396,706
Settlements/repayments	(240,195)		(21,712)		—		—		—		(261,907)
Net proceeds from sales	—		—		—		(19,404)		(70,160)		(89,564)
Transfers	(8,500)		—		—		—		8,500		—
Fair Value as of September 30, 2025	$	622,371	$	150,542	$	333	$	31,214	$	49,553	$	854,013

Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Year Ended September 30, 2024	Secured First Lien Debt		Secured Second Lien Debt		Unsecured Debt		Preferred Equity		Common Equity/ Equivalents		Total
Fair Value as of September 30, 2023	$	510,701	$	127,854	$	24	$	26,855	$	39,128	$	704,562
Total gains (losses):
Net realized gain (loss)(A)	(50)		—		—		332		1,724		2,006
Net unrealized appreciation (depreciation)(B)	(7,071)		2,445		8		(5,039)		52,781		43,124
Reversal of prior period net depreciation (appreciation) on realization(B)	(53)		(22)		—		130		(283)		(228)
New investments, repayments and settlements:(C)
Issuances/originations	131,462		36,978		—		10,150		4,585		183,175
Settlements/repayments	(80,102)		(53,539)		—		—		—		(133,641)
Net proceeds from sales	50		—		—		(1,082)		(1,744)		(2,776)
Transfers	—		—		—		—		—		—
Fair Value as of September 30, 2024	$	554,937	$	113,716	$	32	$	31,346	$	96,191	$	796,222

(A)Included in net realized gain (loss) on investments on our accompanying Consolidated Statements of Operations for the corresponding period.

(B)Included in net unrealized appreciation (depreciation) on investments on our accompanying Consolidated Statements of Operations for the corresponding period.

(C)Includes increases in the cost basis of investments resulting from new portfolio investments, accretion of discounts, PIK, and other non-cash disbursements to portfolio companies, as well as decreases in the cost basis of investments resulting from principal repayments or sales, the amortization of premiums and acquisition costs and other cost-basis adjustments.

Schedule of Investment Holdings

The following table outlines our investments by security type as of September 30, 2025 and 2024:

	September 30, 2025								September 30, 2024
	Cost				Fair Value				Cost				Fair Value
Secured first lien debt	$	646,131	73.7	%	$	622,371	72.4	%	$	580,736	75.3	%	$	554,937	69.7	%
Secured second lien debt	149,937		17.1		150,542		17.5		113,691		14.8		113,716		14.3
Unsecured debt	555		0.1		333		0.1		198		0.0		32		0.0
Total debt investments	796,623		90.9		773,246		90.0		694,625		90.1		668,685		84.0
Preferred equity	37,429		4.3		31,214		3.6		45,017		5.8		31,346		3.9
Common equity/equivalents	42,562		4.8		54,664		6.4		31,369		4.1		96,229		12.1
Total equity investments	79,991		9.1		85,878		10.0		76,386		9.9		127,575		16.0
Total Investments	$	876,614	100.0	%	$	859,124	100.0	%	$	771,011	100.0	%	$	796,260	100.0	%

Our investments at fair value consisted of the following industry classifications as of September 30, 2025 and 2024:

Industry Classification	September 30, 2025				September 30, 2024
	Fair Value		Percentage of Total Investments		Fair Value		Percentage of Total Investments
Healthcare, Education, and Childcare	$	273,262	31.8	%	$	101,707	12.8	%
Diversified/Conglomerate Manufacturing	202,466		23.6		160,264		20.1
Diversified/Conglomerate Service	152,042		17.7		179,032		22.5
Beverage, Food, and Tobacco	54,605		6.4		88,327		11.1
Home and Office Furnishings, Housewares and Durable Consumer Products	30,000		3.5		—		—
Automobile	27,361		3.2		28,286		3.6
Machinery	26,381		3.1		21,816		2.7
Personal, Food, and Miscellaneous Services	23,700		2.7		—		—
Cargo Transportation	20,000		2.3		20,200		2.5
Oil and Gas	17,512		2.0		20,554		2.6
Personal and Non-Durable Consumer Products	13,866		1.6		13,586		1.7
Printing and Publishing	5,809		0.7		4,312		0.5
Aerospace and Defense	1,184		0.1		153,096		19.2
Other, < 2.0%	10,936		1.3		5,080		0.7
Total Investments	$	859,124	100.0	%	$	796,260	100.0	%

Our investments at fair value were included in the following U.S. geographic regions as of September 30, 2025 and 2024:

Location	September 30, 2025				September 30, 2024
	Fair Value		Percentage of Total Investments		Fair Value		Percentage of Total Investments
South	$	287,371	33.5	%	$	314,010	39.4	%
Midwest	237,417		27.6		192,897		24.2
West	233,564		27.2		249,082		31.3
Northeast	100,772		11.7		40,271		5.1
Total Investments	$	859,124	100.0	%	$	796,260	100.0	%

Schedule of Investments Classified by Contractual Maturity Date

The following table summarizes the contractual principal repayment and maturity of our investment portfolio by fiscal year, assuming no voluntary prepayments, as of September 30, 2025:

Year Ending September 30,	Amount
2026(A)	$	58,434
2027	157,554
2028	222,265
2029	139,336
2030	209,608
Thereafter	10,000
Total contractual repayments	$	797,197
Adjustments to cost basis of debt investments	(574)
Investments in equity securities	79,991
Investments held as of September 30, 2025 at cost:	$	876,614

(A)Includes debt investments with contractual principal amounts totaling $0.5 million for which the maturity date has passed as of September 30, 2025.