Statements of Assets, Liabilities and Members' Capital (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2024		Dec. 31, 2023
Statement of Financial Position [Abstract]
Investments, cost	$ 375,695	[1]	$ 85,367	[2]
Deferred financing costs, accumulated amortization	$ 334		$ 68
Common units, issued (in shares)	33,306,325		10,560,000
Common units, outstanding (in shares)	33,306,325		10,560,000

[1] New Mountain Guardian IV Income Fund, L.L.C. (the "Company") generally acquires its investments in private transactions exempt from registration under the Securities Act of 1933, as amended (the "Securities Act"). These investments are generally subject to certain limitations on resale, and may be deemed to be "restricted securities" under the Securities Act.

[2] New Mountain Guardian IV Income Fund, L.L.C. (the "Company") generally acquires its investments in private transactions exempt from registration under the Securities Act of 1933, as amended (the "Securities Act"). These investments are generally subject to certain limitations on resale, and may be deemed to be "restricted securities" under the Securities Act.