(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, the tax so levied shall be refunded to such person in such manner and subject to such conditions as may be provided in any law in force in that State." Clause (b) of section 15 of the Central Act as amended in 1972 retrospectively with effect from 1 10 1958 "(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 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.