"8A. (1) In determining the turnover of a dealer for the purposes of this Act, the following deductions shall be made from the aggregate of the sale prices, namely: —
(a) the amount arrived at by applying the following formula— rate of tax X aggregate of sale prices 100 plus rate of tax
Provided that no deduction on the oasis of the above formula shall be made if the amount by way of tax collected by a registered dealer, in accordance with the provisions of this Act, has been otherwise deducted from the aggregate of sale prices.
Explanation.—Where the turnover of a dealer is taxable at different rates, the aforesaid formula shall be applied separately in respect of each part of the turnover liable to a different rate of tax;
(b) the sale price of all goods returned to the dealer by the purchasers of such goods within a period of three months from the date of delivery of the goods:
Provided that satisfactory evidence of such return of goods and of refund or adjustment in accounts of the sale price thereof is produced before the authority competent to assess or, as the case mav be, re-assess the tax payable by the dealer under this Act; and
(c) such other deductions as the Central Government may, having regard to the prevalent market conditions, facility of trade and interests of consumers, prescribe.
(2) Save as otherwise provided in sub-section (1), in determining the turnover of a dealer for the purposes of this Act, no deduction shall be made from the aggregate of the sale prices.".