In section 239 of the Income-tax Act, for sub-section (2), the following sub-section shall be substituted, namely :-
"(2) No such claim shall be allowed, unless it is made within the period specified hereunder, namely :-
(a) where the claim is in respect of income which is assessable for any assessment year commencing on or before the 1st day of April, 1967, four years from the last day of such assessment year;
(b) where the claim is in respect of income which is assessable for the assessment year commencing on the 1st day of April, 1968, three years from the last day of the assessment year;
(c) where the claim is in respect of income which is assessable for any other assessment year, two years from the last day of such assessment year.".