Rate of Tax: (1) The tax payable by a dealer under this Act shall be levied at the rate of six per cent on his taxable turnover; Provided that the State Government may, from time to time, by notification and subject to such conditions as they may impose, fix a higher rate of tax not exceeding thirteen per cent or any lower tax payable under this Act on account of the sale or purchase of any goods or class of goods specified in such notification; The words "at the rate of six per cent" in the main subsection (I) were substituted for the words "at the rate of five per cent" and the words "not exceeding thirteen per cent" were substituted for the words "not exceeding ten per cent" in the first proviso thereto by the Orissa Sales Tax (Amendment) Act, 1967 (Orissa Act No. 7 of 1976), with effect from May 1, 1976.