27. Adjustment.

When a dealer receives in any year any amount, due to price variation which would have been in his turnover for any previous tax period if it had been received by him during that period, it shall be deemed to be the turnover during the tax period in which such amount was received and he shall, during the tax period in which such amount was received, include such amount in the return separately for the tax period and the assessing authority shall proceed to assess the tax payable on such amount as his turnover of that tax period.