INVESTMENTS IN OPERATING PARTNERSHIPS - Contributions payable (Details) - USD ($)	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2022
INVESTMENTS IN OPERATING PARTNERSHIPS
Capital contributions payable	$ 0	$ 785
Series 29
INVESTMENTS IN OPERATING PARTNERSHIPS
Capital contributions payable	$ 0	$ 785	$ 785

The amount of carrying value of the capital contribution payable to operating partnerships. Under the terms of the Partnership's investment in each Operating Partnership, the Partnership is required to make capital contributions to the Operating Partnerships. These contributions are payable in installments over several years upon each Operating Partnership achieving specified levels of construction and/or operations.

No definition available.

Name:	bctciv_CapitalContributionsPayable
Namespace Prefix:	bctciv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant