Document and Entity Information	6 Months Ended
	Sep. 30, 2023 shares
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	0-26200
Entity Registrant Name	BF GARDEN TAX CREDIT FUND IV L.P.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3208648
Entity Address, Address Line One	225 Franklin Street
Entity Address, Address Line Two	28th Floor
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02110
City Area Code	888
Local Phone Number	773-1487
Title of 12(b) Security	None
No Trading Symbol Flag	true
Security Exchange Name	NONE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	0
Amendment Flag	false
Entity Central Index Key	0000913778
Current Fiscal Year End Date	--03-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2