Borrowings (Tables)

12 Months Ended

Sep. 30, 2025

Debt Disclosure [Abstract]

Schedule of Debt Securitization

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest, average stated interest rates and average outstanding balances for the 2024 Debt Securitization were as follows:

	Year ended September 30,
	2025			2024		2023
Stated interest expense	$	71,193		$	—	$	—
Amortization of debt issuance costs	809			—		—
Total interest and other debt financing expenses	$	72,002		$	—	$	—
Cash paid for interest expense	$	55,072		$	—	$	—
Annualized average stated interest rate	6.0		%	N/A		N/A
Average outstanding balance	$	1,184,625		$	—	$	—

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest, average stated interest rates and average outstanding balances for the 2018 Debt Securitization were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	1,839		$	24,042		$	26,375
Amortization of debt issuance costs	—			2			161
Total interest and other debt financing expenses	$	1,839		$	24,044		$	26,536
Cash paid for interest expense	$	5,152		$	26,430		$	24,271
Average stated interest rate	7.1		%	7.4		%	6.5		%
Average outstanding balance	$	25,881		$	324,648		$	403,098

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest, average stated interest rates and average outstanding balances for the GCIC 2018 Debt Securitization were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	1,682		$	28,062		$	32,923
Accretion of discounts on notes issued	—			—			544
Amortization of debt issuance costs	—			—			21
Total interest and other debt financing expenses	$	1,682		$	28,062		$	33,488
Cash paid for interest expense	$	4,861		$	31,909		$	30,453
Average stated interest rate	6.1		%	6.8		%	6.1		%
Average outstanding balance	$	27,602		$	412,682		$	537,754

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest expense, average stated interest rates and average outstanding balances for the GBDC 3 2021 Debt Securitization were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	2,694		$	7,181		$	—
Amortization of debt issuance costs	—			—			—
Total interest expense	$	2,694		$	7,181		$	—
Cash paid for interest expense	$	7,355		$	2,520		$	—
Average stated interest rate	6.9		%	7.3		%	N/A
Average outstanding balance	$	39,189		$	97,705		$	—

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest expense, average stated interest rates and average outstanding balances for the GBDC 3 2022 Debt Securitization were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	11,364		$	5,909		$	—
Amortization of debt issuance costs	—			—			—
Total interest expense	$	11,364		$	5,909		$	—
Cash paid for interest expense	$	14,765		$	2,508		$	—
Average stated interest rate	6.6		%	7.4		%	N/A
Average outstanding balance	$	173,187		$	79,626		$	—

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest expense, average stated interest rates and average outstanding balances for the GBDC 3 2022-2 Debt Securitization were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	3,504		$	5,923		$	—
Amortization of debt issuance costs	—			—			—
Total interest expense	$	3,504		$	5,923		$	—
Cash paid for interest expense	$	7,197		$	2,229		$	—
Average stated interest rate	7.5		%	8.0		%	N/A
Average outstanding balance	$	46,849		$	73,770		$	—

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest expense, average stated interest rates and average outstanding balances for the “GBDC 3 DB Credit Facility were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	3,820		$	11,219		$	—
Facility fees	244			680			—
Accretion of discounts	—			1			—
Total interest and other debt financing expenses	$	4,064		$	11,900		$	—
Cash paid for interest expense and facility fees	$	11,680		$	4,284		$	—
Average stated interest rate¹	6.7		%	7.6		%	N/A
Average outstanding balance	$	57,154		$	148,365		$	—

(1)The average stated interest rate reflects the translation of the stated interest expense and borrowings in foreign currencies to U.S. dollar.

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest and facility fees, average stated interest rates and average outstanding balances for the JPM Credit Facility were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	69,268		$	26,777		$	41,821
Facility fees	2,820			4,389			2,635
Amortization of debt issuance costs	3,945			3,569			2,793
Total interest and other debt financing expenses	$	76,033		$	34,735		$	47,249
Cash paid for interest expense and facility fees	$	76,080		$	27,612		$	44,667
Average stated interest rate¹	5.7		%	7.1		%	6.2		%
Average outstanding balance	$	1,209,252		$	377,773		$	678,560

(1)The average stated interest rate reflects the translation of the stated interest expense and borrowings in foreign currencies to U.S. dollar.

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest and facility fees, average stated interest rates and average outstanding balances for the 2024 Notes were as follows:

	Year ended September 30,
	2025		2024			2023
Stated interest expense	$	—	$	8,766		$	16,876
Accretion of discounts and amortization of premiums on notes issued	—		(747)			(1,384)
Amortization of debt issuance costs	—		1,140			1,986
Total interest and other debt financing expenses	$	—	$	9,159		$	17,478
Cash paid for interest expense	$	—	$	16,547		$	16,876
Average stated interest rate	N/A		3.4		%	3.4		%
Average outstanding balance	$	—	$	259,563		$	500,000

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest and facility fees, average stated interest rates and average outstanding balances for the 2026 Notes were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	15,000		$	15,000		$	15,000
Accretion of discounts on notes issued	531			532			531
Amortization of debt issuance costs	1,537			1,635			1,493
Total interest and other debt financing expenses	$	17,068		$	17,167		$	17,024
Cash paid for interest expense	$	15,000		$	15,000		$	15,000
Average stated interest rate	2.5		%	2.5		%	2.5		%
Average outstanding balance	$	600,000		$	600,000		$	600,000

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest and facility fees, average stated interest rates and average outstanding balances for the 2027 Notes were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	7,176		$	7,176		$	7,176
Accretion of discounts on notes issued	732			736			733
Amortization of debt issuance costs	840			1,021			926
Total interest and other debt financing expenses	$	8,748		$	8,933		$	8,835
Cash paid for interest expense	$	7,176		$	7,176		$	7,174
Average stated interest rate	2.1		%	2.1		%	2.1		%
Average outstanding balance	$	350,000		$	350,000		$	350,000

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest and facility fees, average stated interest rates and average outstanding balances for the 2028 Notes were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	31,969		$	26,084		$	—
Net contractual interest rate swap expense	1,358			3,775			—
Net (gain)/loss related to the fair value hedge	7,398			(7,549)			—
Accretion of discounts on notes issued	904			795			—
Amortization of debt issuance costs	1,216			975			—
Total interest and other debt financing expenses	$	42,845		$	24,080		$	—
Cash paid (received) for interest expense(1)	$	27,920		$	20,005		$	—
Annualized average interest rate swap and stated interest rate(2)	7.4		%	8.1		%	N/A
Average outstanding balance	$	453,425		$	370,082		$	—

(1)Includes cash paid or received for contractual interest rate swaps, which may have different contractual settlement dates among the (i) fixed interest leg, (ii) floating interest leg and (iii) the 2028 Notes.

(2) The annualized average stated interest rate reflects the translation of the stated interest expense and borrowings in foreign currencies to U.S. dollars.

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest and facility fees, average stated interest rates and average outstanding balances for the 2029 Notes were as follows:

	Year ended September 30,
	2025			2024			2023
Stated interest expense	$	43,450		$	24,000		$	—
Net contractual interest rate swap expense	5,345			6,631			—
Net (gain)/loss related to the fair value hedge	(2,842)			2,951			—
Accretion of discounts on notes issued	1,116			826			—
Amortization of debt issuance costs	1,649			895			—
Total interest and other debt financing expenses	$	48,718		$	35,303		$	—
Cash paid (received) for interest expense (1)	$	47,971		$	23,846		$	—
Annualized average interest rate swap and stated interest rate (2)	6.7		%	7.6		%	N/A
Average outstanding balance	$	724,110		$	398,361		$	—

(1)Includes cash paid or received for contractual interest rate swaps, which may have different contractual settlement dates among the (i) fixed interest leg, (ii) floating interest leg and (iii) the 2029 Notes.

(2)     The annualized average stated interest rate reflects the translation of the stated interest expense and borrowings in foreign currencies to U.S. dollars.

For the years ended September 30, 2025, 2024 and 2023, the components of interest expense, cash paid for interest, average stated interest rates and average outstanding balances for the Adviser Revolver were as follows:

	Year ended September 30,
	2025			2024		2023
Stated interest expense	$	57		$	—	$	—
Cash paid for interest expense	—			—		—
Average stated interest rate	3.9		%	N/A		N/A
Average outstanding balance	$	1,438		$	—	$	—

Schedule of Interest Rate and Interest Differential Analysis

As of September 30, 2025, the classes, amounts, ratings and interest rates in effect (expressed as a spread to three-month SOFR) of the Class A-1R and A-2RR 2024 Notes are as follows:

Description	Class A-1R 2024 Notes	Class A-2RR 2024 Notes
Type	Senior Secured Floating Rate	Senior Secured Floating Rate
Amount Outstanding	$1,192,400	$171,600
Fitch Rating	“AAA”	“NR”
S&P Rating	“AAA”	“AAA”
Interest Rate	SOFR + 1.56%	SOFR + 1.75%

Schedule of Maturities of Long-Term Debt

A summary of the Company’s maturity requirements for borrowings as of September 30, 2025 is as follows:

	Payments Due by Period
	Total		Less Than 1 Year		1 – 3 Years		3 – 5 Years		More Than 5 Years
2024 Debt Securitization	1,364,000		—		—		—		1,364,000
JPM Credit Facility	1,098,437		—		—		1,098,437		—
Adviser Revolver	39,200		—		—		—		39,200
2026 Notes(1)	599,524		599,524		—		—		—
2027 Notes(1)	348,994		—		348,994		—		—
2028 Notes(1)(2)	720,521		—		—		720,521		—
2029 Notes(1)(2)	756,102		—		—		756,102		—
Total borrowings	$	4,926,778	$	599,524	$	348,994	$	2,575,060	$	1,403,200

(1) Represents principal outstanding plus unamortized premium and / or unaccreted original issue discount.

(2) Carrying value is inclusive of an adjustment for the change in fair value of an effective hedge accounting relationship. See Note 5 for additional information.