Gladstone Capital Corporation Annual report pursuant to Section 13 and 15(d)

Annual report pursuant to Section 13 and 15(d)

RELATED PARTY TRANSACTIONS - Narrative (Details)

RELATED PARTY TRANSACTIONS - Narrative (Details) - USD ($)	6 Months Ended	12 Months Ended											24 Months Ended	36 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2022	Mar. 31, 2023
Related Party Transaction [Line Items]
Base management fee		1.75%
Base management fee, percent fee		100.00%
Investment company, excess expense reimbursable		$ 0		$ 8,000	$ 100,000
Management and service fee, net of credit		0.50%		0.50%
Management and service fees, loans		1.50%
Ratio of net investment income (loss) to average net assets – annualized		8.49%		6.61%	6.40%	6.11%	6.74%	6.41%	6.13%	6.90%	5.55%	6.37%
Incentive fee base on minimum rate of return required on investment		$ 0
Percentage of pre-incentive fee net investment income is less than the hurdle rate		100.00%
Investment company, pre-incentive fee net investment income, percent threshold of net assets	2.1875%		2.50%										2.4375%
Pre-incentive fee net investment income exceeds the hurdle rate		20.00%
Investment company, capital gains-based incentive fees	20.00%	20.00%
Investment company, net investment income to common stockholder distributions ratio, threshold		100.00%		100.00%	100.00%
Incentive fee credit		$ 0		$ 437,000	$ 451,000
Success fee income		935,000		4,794,000	202,000
Investment company, other operating expenses, due to advisor	$ 65,000	65,000		44,000
Related Party
Related Party Transaction [Line Items]
Success fee income		800,000		1,100,000	$ 800,000
Fees due to related party	4,351,000	4,351,000		2,527,000
Related Party \| Gladstone Investment Corporation
Related Party Transaction [Line Items]
Fees due to related party	$ 19,000	$ 19,000		$ 13,000
Adviser \| Related Party \| Chief Executive Officer
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by parent	100.00%	100.00%
Administrator \| Related Party \| Chief Executive Officer
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by parent	100.00%	100.00%
Gladstone Securities, LLC \| Related Party \| Chief Executive Officer
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by parent	100.00%	100.00%
Maximum
Related Party Transaction [Line Items]
Base management fee		1.75%
Minimum
Related Party Transaction [Line Items]
Ratio of net investment income (loss) to average net assets – annualized	1.75%													2.00%