N-2
Mar. 31, 2023
Cover [Abstract]  
Entity Central Index Key 0001562818
Amendment Flag false
Securities Act File Number 333-262119
Investment Company Act File Number 811-22774
Document Type N-2
Document Registration Statement true
Pre-Effective Amendment false
Post-Effective Amendment true
Post-Effective Amendment Number 2
Investment Company Act Registration true
Investment Company Registration Amendment true
Investment Company Registration Amendment Number 9
Entity Registrant Name BlackRock Multi-Sector Income Trust
Entity Address, Address Line One 100 Bellevue Parkway
Entity Address, City or Town Wilmington
Entity Address, State or Province DE
Entity Address, Postal Zip Code 19809
City Area Code 800
Local Phone Number 882‑0052
Approximate Date of Commencement of Proposed Sale to Public From time to time after the effective date of this Registration Statement.
Dividend or Interest Reinvestment Plan Only false
Delayed or Continuous Offering true
Primary Shelf [Flag] true
Effective Upon Filing, 462(e) false
Additional Securities Effective, 413(b) false
Effective when Declared, Section 8(c) false
New Effective Date for Previous Filing false
Additional Securities. 462(b) false
No Substantive Changes, 462(c) false
Exhibits Only, 462(d) true
Exhibits Only, 462(d), File Number 333-262119
Registered Closed-End Fund [Flag] true
Business Development Company [Flag] false
Interval Fund [Flag] false
Primary Shelf Qualified [Flag] true
Entity Well-known Seasoned Issuer No
Entity Emerging Growth Company false
New CEF or BDC Registrant [Flag] false
Business Contact [Member]  
Cover [Abstract]  
Entity Address, Address Line One 50 Hudson Yards
Entity Address, City or Town New York
Entity Address, State or Province NY
Entity Address, Postal Zip Code 10001
Contact Personnel Name John M. Perlowski, President