In terms of Section 34(1) of the CGST Act, 2017 in case of return of goods on which GST was paid at the time of supply, the supplier of such goods may issue a credit note for the full value, including the amount of GST in favour of the recipient, and will be entitled to reduce his output tax liability subject to the condition that the recipient of such supply has not availed credit of such GST and if availed, has reversed his ITC on the same.
(FAQ 34: MINING)