Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 10, 2021	Jun. 30, 2020
Details
Registrant CIK	0000355573
Fiscal Year End	--12-31
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	000-12439
Entity Registrant Name	REAL ESTATE ASSOCIATES LIMITED IV
Entity Incorporation, State or Country Code	CA
Entity Tax Identification Number	95-3718731
Entity Address, Address Line One	PO Box 91274
Entity Address, City or Town	Los Angeles
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	90009
Entity Address, Address Description	Address of principal executive offices
City Area Code	720
Local Phone Number	387-8135
Phone Fax Number Description	Registrant’s telephone number, including area code
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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 Public Float			$ 0
Entity Common Stock, Shares Outstanding		6,496.11
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY