GSTR-3B Will Not Let You Edit Sales: Fixing a GSTR-1 Mistake With GSTR-1A
Since the July 2025 tax period, the sales tax that GSTR-3B fills in from GSTR-1 cannot be edited. To fix a mistake, file GSTR-1A for the same month after GSTR-1 and before GSTR-3B. If both returns are already filed, amend the invoice in the next GSTR-1 and pay any extra tax with interest.
For years, accountants fixed sales mistakes in GSTR-3B. A missed invoice or a wrong figure in GSTR-1 was simply corrected in the summary return, and GSTR-1 was tidied up later. That no longer works.
What changed
From the July 2025 tax period, the tax on sales that GSTR-3B fills in automatically from GSTR-1 (and from the Invoice Furnishing Facility, IFF) is locked. You cannot type over it. GSTN calls this hard-locking.
GSTR-1 is now the single source of truth for your sales tax. If GSTR-1 is wrong, GSTR-3B will be wrong in the same way, unless you correct GSTR-1 first.
The interstate supplies table (Table 3.2) was announced for locking and then deferred. Check the portal for its current status before you rely on editing it.
GSTR-1A: the correction form
GSTR-1A is an optional form for the same tax period, filed after GSTR-1 and before GSTR-3B. You can use it to:
- ✓add invoices you left out of GSTR-1;
- ✓correct invoices, credit notes or debit notes reported in that period's GSTR-1.
Once you file GSTR-1A, the corrected figures flow into GSTR-3B.
What to do in each situation
| Where you are | How to fix the mistake |
|---|---|
| GSTR-1 not yet filed | Correct the invoice before you file |
| GSTR-1 filed, GSTR-3B not filed | File GSTR-1A for the same month, then GSTR-3B |
| Both filed | Amend the invoice in the next month's GSTR-1, and pay any extra tax with interest |
| Tax underpaid and noticed much later | Amend in GSTR-1 and pay the difference through DRC-03, with interest |
A worked example
A Coimbatore pump spares dealer files GSTR-1 for August 2026 on 11 September. On 15 September the accountant finds a ₹2,50,000 invoice (₹45,000 GST) that was left out. GSTR-3B is due on the 20th.
- ✓The old way: add ₹45,000 in GSTR-3B by hand. That is not possible now.
- ✓The new way: file GSTR-1A for August with the missing invoice. GSTR-3B then shows the correct tax, and the buyer gets the invoice in IMS for their credit.
A monthly order of work
- Close the sales register for the month.
- Reconcile it with e-invoices and e-way bills.
- File GSTR-1 (by the 11th for monthly filers).
- Check IMS for rejections by your buyers.
- File GSTR-1A if anything needs correcting.
- File GSTR-3B (by the 20th for monthly filers).
Frequently asked questions
Is GSTR-1A compulsory?
No. You file it only when you need to correct or add something for that period.
Can I reduce my tax in GSTR-1A?
Yes, by correcting a wrong invoice. But a reduction because goods were returned or a discount was given should be made with a credit note.
Is the credit in GSTR-3B locked too?
Credit is auto-filled from GSTR-2B. GSTN has indicated it may lock that too in future. Until it does, claim credit only as supported by GSTR-2B.
Sources
- ✓Hard-locking of auto-populated values in GSTR-3B, ClearTax
- ✓Hard-locking GSTR-3B: a new compliance milestone and its pitfalls, Lakshmikumaran & Sridharan
- ✓GSTN advisory on hard-locking in GSTR-3B, EY
This is a summary, not legal advice. Confirm with your chartered accountant before you rely on it.
Written by
Founder, Airwix Technologies (Sleet)
Vatsal Sutariya is the founder of Airwix Technologies in Ahmedabad, the company that builds Sleet: SleetHR for HR and payroll, and Sleet Accounting for GST billing and books. He writes about GST, invoicing, business tax and choosing software for Indian businesses, and checks each rule against the official notification before it is published.
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