No tax payable
in case of inter-State trade etc.4. Notwithstanding anything contained in this Act, a tax on the sale or purchase of goods shall not be imposed under this Act, -
(a) where such sale or purchase takes place outside the State;
(b) where such sale or purchase takes place in the course of import of the goods into, or export of the goods out of, the territory of India; or
(c) where such sale or purchase takes place in the course of inter-State trade or commerce.