Question 9 - Sales return under CST (i.e. Central Sales Tax Act) is allowable as deduction from the turnover within six months? If, say, goods are returned in GST regime by a buyer within six months from appointed day, will it become taxable in GST? - FAQ on GST (2nd Edition) dated 31.3.2017

Q 9. Sales return under CST (i.e. Central Sales Tax Act) is allowable as deduction from the turnover within six months? If, say, goods are returned in GST regime by a buyer within six months from appointed day, will it become taxable in GST? Ans. Where tax has been paid under the existing law [CST, in this case] on any goods at the time of sale, not being earlier than six months prior to the appointed day, and such goods are returned by the buyer after the appointed day, the sales return will be considered as a supply of the said buyer in GST and tax has to be paid on such supply, if, (i) the goods are taxable under the GST Law; and (ii) the buyer is registered under the GST Law. However, the seller is entitled to refund of such tax [CST, in this case] paid under the existing law if the aforesaid buyer is an unregistered person under GST and the goods are returned within 06(six) months (or within the extended period of maximum two months) from the appointed day and the goods are identifiable - Section 142(1).