INVESTMENTS IN OPERATING PARTNERSHIPS - Current financial results available for the Operating Partnerships (Details) - USD ($)	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Revenues
Rental	$ 753,172	$ 1,273,851
Interest and other	15,959	33,464
Operating Partnerships Revenues	769,131	1,307,315
Expenses
Interest	77,827	202,002
Depreciation and amortization	155,336	311,636
Operating expenses	543,904	995,009
Operating Partnerships Total Expenses	777,067	1,508,647
NET INCOME (LOSS)	(7,936)	(201,332)
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	(7,857)	(199,319)
Net income (loss) allocated to other Partners	(79)	(2,013)
Series 20
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 21
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 22
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 23
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 24
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 25
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 26
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 27
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 28
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 29
Revenues
Rental	0	162,975
Interest and other	0
Operating Partnerships Revenues	0	162,975
Expenses
Interest	0	12,230
Depreciation and amortization	0	27,154
Operating expenses	0	159,531
Operating Partnerships Total Expenses	0	198,915
NET INCOME (LOSS)	0	(35,940)
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	(35,581)
Net income (loss) allocated to other Partners	0	(359)
Series 30
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 31
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 32
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 33
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 34
Revenues
Rental	313,380	297,031
Interest and other	11,974	17,954
Operating Partnerships Revenues	325,354	314,985
Expenses
Interest	41,931	42,952
Depreciation and amortization	44,215	43,289
Operating expenses	225,447	184,147
Operating Partnerships Total Expenses	311,593	270,388
NET INCOME (LOSS)	13,761	44,597
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	13,623	44,151
Net income (loss) allocated to other Partners	138	446
Series 35
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 36
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 37
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 38
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 39
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 40
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 41
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 42
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 43
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 44
Revenues
Rental	0	0
Interest and other	0	0
Operating Partnerships Revenues	0	0
Expenses
Interest	0	0
Depreciation and amortization	0	0
Operating expenses	0	0
Operating Partnerships Total Expenses	0	0
NET INCOME (LOSS)	0	0
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	0
Net income (loss) allocated to other Partners	0	0
Series 45
Revenues
Rental	0	66,559
Interest and other	0	823
Operating Partnerships Revenues	0	67,382
Expenses
Interest	0	21,885
Depreciation and amortization	0	27,408
Operating expenses	0	97,274
Operating Partnerships Total Expenses	0	146,567
NET INCOME (LOSS)	0	(79,185)
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	0	(78,393)
Net income (loss) allocated to other Partners	0	(792)
Series 46
Revenues
Rental	439,792	747,286
Interest and other	3,985	14,687
Operating Partnerships Revenues	443,777	761,973
Expenses
Interest	35,896	124,935
Depreciation and amortization	111,121	213,785
Operating expenses	318,457	554,057
Operating Partnerships Total Expenses	465,474	892,777
NET INCOME (LOSS)	(21,697)	(130,804)
Net income (loss) allocated to BF Garden Tax Credit Fund IV L.P.	(21,480)	(129,496)
Net income (loss) allocated to other Partners	$ (217)	$ (1,308)