12. (1) The amount of the excess profits tax payable in respect of a business for any chargeable accounting period diminished by any amount allowable by way of relief under the provisions of section 11, or section 11A shall, in computing for the purposes of income tax or super tax the profits and gains of that business, be allowed to be deducted as an expense incurred in that period. (2) There shall also be so deducted the amount of any excess profits tax payable under any law in force in a ¹[* * *] country outside the taxable territories on the profits of the business in respect of any chargeable accounting period to the extent to which such profits are liable to excess profits tax under this Act after diminishing such amount by any amount which is allowable by way of relief by repayment, set off or, otherwise under any law in the ²[* * *] country where the tax is payable providing for the granting of relief in that ³[* * *] country where excess profits tax has also been charged in the taxable territories: Provided that where, under the provisions of this Act relating to deficiencies of profits or under any corresponding law in force in the said ⁴[* * *] country without the taxable territories, relief is given by way of repayment from excess profits tax chargeable for any chargeable accounting period previous to that in which the deficiency occurs, the amount of the deduction allowed under sub section (1) or sub section (2) shall not be altered, but the amount repayable shall be taken into account in computing the profits and gains of the business for the purposes of income tax as if it were a profit of the business accruing in the previous year (as determined for that business for the purposes of the Income tax Act, 1922), in which the deficiency of profits occurs.