How to correct a mistake in a filed return

Filed GST returns cannot be edited after submission. You fix mistakes by amending in a later period's return.

How it works

GSTR-1 has amendment tables where you correct an earlier invoice's details. Tax shortfalls from an error are paid with interest in GSTR-3B. Most corrections for a financial year must be done by the deadline (generally the return for September of the next year, or the annual return, whichever is earlier).

The cleaner habit is to reconcile before filing. See matching books to the portal.