(1) Subject to the provisions of sub-section (2), in computing the chargeable interest of a previous year, there shall be allowed from the total amount of interest (other than interest on loans and advances made to ¹[credit institutions] accruing or arising to the assessee in the previous year, a deduction in respect of the amount of interest which is established to have become a bad debt during the previous year:
     Provided that such interest has been taken into account in computing the chargeable interest of the assessee of an earlier previous year and the amount has been written off as irrecoverable in the accounts of the assessee for the previous year during which it is established to have become a bad debt.
     Explanation.--For the removal of doubts, it is hereby declared that in computing the chargeable interest of a previous year, no deduction, other than the deduction specified in this sub-section, shall be allowed from the total amount of interest accruing or arising to the assessee.
     (2) In computing the chargeable interest of a previous year, the amount of interest which accrues or arises to the assesse ²[before the 1st day of August, 1974 or ³[during the period commencing on the 1st day of April, 1985 and ending with the 30th day of September, 1991] shall not be taken into account.