(1) The tax payable by a dealer under section 3 shall be levied on his taxable turnover of sales.

(2) Taxable turnover of sales in relation to a dealer liable to pay tax under sub-section (1) of section 3 shall be calculated from the gross turnover of sales during any period which remains after deducting there from -

(a) sales of goods declared as exempt from tax in schedule III;

(b) sales of goods which are shown to the satisfaction of the Commissioner to have taken place -

(i) in the course of inter-State trade or commerce, or

(ii) outside Tripura.

(iii) in the course of export of the goods out of the territory of India.

Explanation - Section 3, 4 and 5 of the Central Sales Tax Act, 1956 shall apply for determining whether or not a particular sale or purchase has taken place in the manner indicated in sub-clause (i), sub-clause (ii) or sub-clause(iii).

(c) in case of turnover of sales in relation to works contract, the charges towards labour, services and other like charges and subject to such conditions as may be prescribed;

Provided that in cases where the amount of charges towards labour, services and other like charges in such contract are not ascertainable from the terms and conditions of the contract, the amount of such charges shall be calculated at the prescribed percentage.

(d) such other sales on such conditions and restrictions as may be prescribed.