Bihar Board 12th Supplementary Form 2023 Last Date Extended: The Bihar School Examination Board (BSEB) has extended the last date for registrations for the Bihar Board 12th Supplementary Exam 2023 on its official website. Students who are not happy with their marks or did not secure the minimum passing marks in the Bihar Board 12th result can now apply for a supplementary exam until March 30, 2023, on the official website of the BSEB, biharboardonline.bihar.gov.in.