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DISTRIBUTIONS TO COMMON STOCKHOLDERS - Schedule of Components of Our Net Assets on a Tax Basis (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022
--- | --- | --- | --- | ---
Equity [Abstract] |  |  |  |  |
Common stock | [1] | $ 45 | $ 44 |  |
Capital in excess of par value |  | 501,628 | 492,305 |  |
Cumulative net unrealized appreciation (depreciation) of investments |  | (17,490) | 25,249 |  |
Undistributed ordinary income |  | 5,481 | 6,590 | $ 5,000 |
Undistributed capital gain |  | 717 | 0 |  |
Capital loss carryforward |  | 0 | (47,435) |  |
Other temporary differences |  | (8,346) | (5,858) |  |
TOTAL NET ASSETS |  | $ 482,035 | $ 470,895 | $ 408,695 | $ 315,487
[1] | Issued and outstanding shares of common stock and net asset value per share have been adjusted on a retroactive basis to reflect the 1-for-2 reverse stock split (the “Reverse Stock Split”) effected on April 4, 2024. Refer to Note 2—Summary of Significant Accounting Policies for additional information.

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