Where a dealer makes sales of any pre-used motor vehicles including two wheelers like motor cycle, scooter, etc., to any person, whether a dealer or not, such dealer may, for the purpose of

determination of his turnover of sales on which tax is payable, deduct under clause (c) of sub-section (1) of section 16, from his turnover of sales fifty per centum of that part of turnover of sales which represents sales of such vehicles including two wheelers and he shall, on demand by the appropriate authority under the Act, furnish the relevant tax invoice or invoice or cash memo or bill and other related documents evidencing such sale:

Provided that no such deduction shall be allowed unless the registered dealer selling the goods, on demand by the appropriate authority under the Act, furnishes the relevant tax invoice or invoice or cash memo or bill, and other related documents evidencing such sale.