Section 4(2) in The Punjab General Sales Tax (Amendment and Validation) Act, 1987
(2)Notwithstandings anything contained in sub-section (1), any supply of the nature referred to therein shall be exempt from the aforesaid tax,-(a)where such supply has been made by any restaurant or eating house (by whatever name called) at any time on or after the 7th day of September, 1978 and before the commencement of the Punjab General Sales Tax (Amendment) Act, 1987 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 , or(b)where such supply, not being any such supply by any restaurant or eating house (by whatever name called), has been made at any time on 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:Provided that the burden of proving that the aforesaid tax was not collected on any supply of the nature referred to in clause (a) or, as the case may be, clause (b), shall be on the person claiming the exemption under this sub-section.
