Amendment to income tax provision inserts a prior-period cutoff clarifying transitional applicability, effective on enactment commencement. The Finance Act, 1992 amends section 23(1) by inserting the words 'but before the 1st day of April, 1992' after '31st day of March, 1982' in clause (d) of the second proviso, with effect from the 1st day of April, 1993, thereby establishing a prior-period cutoff within that proviso.