In section 43B of the Income-tax Act, before the Explanation, the following provisos shall be inserted with effect from the 1st day of April, 1988, namely :-
"Provided that nothing contained in this section shall apply in relation to any sum referred to in clause (a) which is actually paid by the assessee on or before the due date applicable in his case for furnishing the return of income under sub-section (1) of section 139 in respect of the previous year in which the liability to pay such sum was incurred as aforesaid and the evidence of such payment is furnished by the assessee along with such return :
Provided further that no deduction shall, in respect of any sum referred to in clause (b), be allowed unless such sum has actually been paid during the previous year on or before the due date as defined in the Explanation below clause (va) of sub-section (1) of section 36."