Every sales tax law of State shall, in so far as it imposes or authorises the imposition of a tax on the sale or pur chase of declared goods, be subject to the following restrictions and conditions, namely: (a) the tax payable under that law in respect of any sale or purchase of such goods inside the State shall not exceed four per cent of the sale or purchase price thereof, and such tax shall not be levied at more than one stage; (b) where a tax has been levied under that law in respect of the sale or purchase inside the State of any declared goods and such goods are sold in the course of Inter State trade or commerce, and tax has been paid under this Act in respect of the sale of such goods in the course of Inter State trade or commerce, the tax levied under such law shall be 334 reimbursed to the person making such sale in the course of Inter State trade or commerce, in such manner and subject to such conditions as may be provided in any law in force in that State; (c) where a tax has been levied under that law in respect of the sale or purchase inside the State of any paddy referred to in sub clause (i) of clause (i) of section 14, the tax leviable on rice procured out of such paddy shall be reduced by the amount of tax levied on such paddy; (d) each of the pulses referred to in clause (vi a) of section 14, whether whole or separated, and whether with or without husk, shall be treated as a single commodity for the purposes of levy of tax under that law.