Partner - Audit & Assistance
4825 Points
Joined December 2018
In either case, as GST returns already filed for the month, credit note can be filed (within time limit mentioned in Sec 34) to reverse the taxes and taxable value. Disclose in GSTR 1 (for regd. CN - CDNR sheet, for unregd. CN - Net off in B2C).
Whether payment is made or not would not have an impact, as one it is cancelled amount would have to be returned.