02 July 2021
3B cannot be revised but you can adjust the sales in next months 3B, if bill cancelled after filing GSTR-1 is of B2B supplies, then while filing next months GSTR-1 amend the said bill in amended B2B details and if pertains to B2C only then you cna amend B2c accordingly.
02 July 2021
Yes you can. File credit note in the next gstr-1 and don't take that effect in next gstr-3b since you are already adjusting that in present gstr3b