Section 31(2)(b) in Punjab General Sales Tax Act, 1948
(b)where such supply, not being any such supply by any restaurant or eating house (by whatever name called) has been made before at any time or after the 4th day of January, 1972, and before such commencement and the aforesaid tax has not been collected on such supply on the ground that no such tax could have been levied or collected at that time :