In this Act, unless the context otherwise requires,-

(40) "Turnover of sales", in relation to any period, means the aggregate of the sale-prices or parts of sale-prices receivable by a dealer, or if a dealer so elects, actually received by the dealer, during such period after deducting therefrom-
(a) the sale prices or the parts of sale-prices, if any, in respect of sale during such period of, goods specified in Schedule IV other than rice, wheat and country liquor as specified in that Schedule, which are shown to the satisfaction of the Commissioner to have been purchased by the dealer in West Bengal, but excluding such sales as the State Government may, by Notification, specify
(b) the amounts, if any, refunded by the dealer in respect of any goods returned by the purchaser within such period, and
(c) the amounts, charged as surcharge payable under section 16 and the amounts charged as additional surcharge payable under Section 16A and the amounts charged as turnover tax payable under Section 16B during such period:
PROVIDED that an election as aforesaid once made shall not be altered except with the permission of the Commissioner and on such terms and conditions as he may think fit to impose;
(d) the sale-prices or the parts of sale-prices if any, in respect of sale during such period of goods specified in Schedule VIII, on a prior sale whereof in West Bengal by a registered dealer, who is an importer, or a manufacturer and is not entitled to enjoy the benefit of exemption from payment of tax, or deferment of payment of tax, or remission of tax payable, under section 39, section 40, section 41, section 42, or section 43, of such goods, tax is shown to the satisfaction of the Commissioner to have been paid at the rate referred to in section 22D;