for the refund was made, if the tax period for the person claiming refund is a quarter; or (b) carried forward to the next tax period as a tax credit in that period. (4) Where the Commissioner has issued a notice to the person under section 58 of this Act advising him that an audit, investigation or inquiry into his business affairs will be undertaken or sought additional information under section 59 of this Act, the amount shall be carried forward to the next tax period as a tax credit in that period. (5) The Commissioner may, as a condition of the payment of a refund, demand security from the person pursuant to the powers conferred in section 25 of this Act within fifteen days from the date on which the return was furnished or claim for the refund was made. (6) The Commissioner shall grant refund within fifteen days from the date the dealer furnishes the security to his satisfaction under sub- section (5). (7) For calculating the period prescribed in clause (a) of sub- section (3),