A method and system for processing buffer status reports (BSRs) such that when BSR triggering is performed, the size(s) of the necessary sub-header(s) are also to be considered together in addition to the BSR size. The steps of checking whether any padding region is available in a MAC PDU that was constructed, comparing the number of padding bits with the size of the BSR plus its sub-header, and if the number of padding bits is larger than the size of the BSR plus its sub-header, triggering BSR are performed. Doing so allows the sub-header(s) to be inserted or included into the MAC PDU or transport block (TB) or other type of data unit.