Where M/s. Garden Reach Shipbuilders and Engneers Limited, Kolkata (hereinafter referred to as GRSE), makes sales, on or after the 1st day of April, 2005, to Indian Navy, Government of India, Ministry of Defence, of vessel constructed by it on the basis of cost plus remuneration contract, the GRSE 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 its turnover of sales that part of such turnover of sales which represents sales of such vessel:

Provided that no such deduction shall be allowed unless the 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 along with a copy of such contract.