The Bank Branch code or BSR code is a 7-digitcode allotted to banks by RBI. This is different from the branch code, which is used for bank drafts etc. This number is given in the OLTAS challan or can be obtained either from the bank branch or from the search facility at NSDL-TIN website. It is mandatory to quote the BSR code both in the challan and deductee details. Hence, this field cannot be left blank. Government deductors however, transfer their tax by a book entry system, in which case the BSR code can be left blank.