What Is GSTR-1A?

GSTR-1A is an amendment form under GST that lets a supplier correct or add invoice details in their already-filed GSTR-1, before they file GSTR-3B for the same tax period. Think of it as a short correction window — available after your GSTR-1 is filed, but only until you file your GSTR-3B. Once you pay your tax liability through GSTR-3B, that window closes permanently for that period.

The Key Rule: Current Period Only

This is where most people get confused. GSTR-1A can only be used to amend or add data that belongs to the current tax period's GSTR-1. It cannot be used to fix invoices or data from previous months or quarters.

Situation Correctable in GSTR-1A?
Mistake in April 2026 GSTR-1, and April 2026 GSTR-3B not yet filed Yes
Missed invoice of the current month Yes
Amendment to an invoice from a previous month already filed No
Correction after filing GSTR-3B of the same period No

The Time Window

GSTR-1A becomes available after the filing date (or due date) of your GSTR-1 for that period. It closes the moment you file your GSTR-3B for the same period. This window can be short — sometimes just a few days — so if you spot an error, act quickly.

A Practical Example

Let's say your GSTR-1 for April 2026 was filed on 11 May 2026. Shortly after, you realise you forgot to include one invoice. Since your April 2026 GSTR-3B is not yet filed, you can add that invoice through GSTR-1A. The corrected data will automatically flow into your GSTR-3B liability.

However, if you also noticed an error in a March 2026 invoice, GSTR-1A cannot help you there. March belongs to a past period — that correction must be done through the amendment tables in a future GSTR-1 (typically the next month's return).

Quick Summary

  • GSTR-1A is optional — you are not required to file it.
  • It can generally be filed once per tax period.
  • Any changes made through GSTR-1A auto-populate into GSTR-3B liability of the same period, so your tax outgo adjusts automatically.
  • For previous period corrections, use the amendment tables in your next GSTR-1 — not GSTR-1A.

Have questions about a specific GST correction situation? Reach out to ASA and Company for a free consultation. We help businesses across Jaipur and India navigate GST compliance correctly the first time — and fix it cleanly when something goes wrong.