Wrong invoice filed in GSTR 1

If you've mistakenly filed GSTR 1 with an excess amount on an invoice and paid the tax, you can rectify this. The primary method is to issue a credit note to the customer for the differential amount. This credit note will reflect in the customer's GSTR-2B, allowing them to reduce their Input Tax Credit (ITC). You can then reduce your own tax liability in subsequent GSTR-3B returns by the excess amount paid. Alternatively, if the invoice itself was correct but reported incorrectly, you can file an amendment in your next GSTR-1.