Determination of turnover: allowable deductions for tax-inclusive sales, returned goods, and government-prescribed items under the Act. Determination of turnover under Section 8A allows only specified deductions from a dealer's aggregate sale prices: a tax-inclusive deduction computed by a prescribed formula (applied separately to turnover at different rates) unless tax has already been deducted; the sale price of returned goods where supported by evidence and within prescribed timeframes; and other deductions as prescribed by the Central Government. No other deductions may be made.