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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Mar. 31, 2024 USD ($) investment loan | Mar. 31, 2023 USD ($) | Mar. 31, 2024 USD ($) investment loan | Mar. 31, 2023 USD ($) | Sep. 30, 2023 USD ($) loan investment
Summary of Investment Holdings [Line Items] |  |  |  |  |  |
Cost | $ 790,542 |  | $ 790,542 |  | $ 722,269 | [1]
Fair Value | 791,588 |  | 791,588 |  | 704,815 | [1]
Total interest income (excluding PIK interest income) | 22,330 | $ 18,803 | 43,918 | $ 36,172 |  |
PIK interest income | 1,385 | 775 | 2,793 | 1,773 |  |
OID |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |
Fair Value | $ 900 |  | $ 900 |  | $ 700 |
Number of loans | loan | 3 |  | 3 |  | 4 |
Total interest income (excluding PIK interest income) | $ 100 | 100 | $ 100 | 100 |  |
PIK |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |
Number of investments | investment | 11 |  | 11 |  | 8 |
Proceeds from interest received | $ 0 | $ 0 | $ 0 | $ 400 |  |
Edge Adhesives Holdings, Inc. |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |
Cost | $ 20,400 |  | $ 20,400 |  | $ 6,100 |
Cost percentage | 2.80% |  | 2.80% |  | 0.90% |
Fair Value | $ 12,900 |  | $ 12,900 |  | $ 2,900 |
Fair value percentage | 1.80% |  | 1.80% |  | 0.50% |
[1] | Cumulative gross unrealized depreciation for federal income tax purposes is $56.9 million; cumulative gross unrealized appreciation for federal income tax purposes is $33.7 million. Cumulative net unrealized depreciation is $23.2 million, based on a tax cost of $728.0 million.

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