Time limit for block assessment: prescribed quarters and excluded interruption periods determine extensions and computation. Section 158BE fixes the time-limit for passing block assessment orders arising from searches or requisitions: generally twelve months from the end of the quarter in which the last authorisation was executed, subject to extensions where a transfer pricing reference is made and where return filing is extended by thirty days. The same period applies to assessments of other persons served under section 158BD. The computation excludes specified interruption periods (including up to 180 days during transfer of seized/requisitioned material, stays, treaty information exchanges, audit and valuation processes, valuation officer reports, central approvals, and advance ruling processes); residual periods under sixty days are extended to sixty days and expiry before month end is extended to month end.