How GSTR-3B works — and why it is now locked to GSTR-1
Written by Tax Paramarsh editorial teamReviewed by Tax Paramarsh GST deskLast updated 3 October 2026Applies to: GST rules in force on 3 October 2026
GSTR-3B is the summary return where you declare your tax, claim input tax credit and pay the balance. Since the July 2025 return period, the tax liability in it comes straight from GSTR-1 and can’t be edited.
What goes into GSTR-3B
- Output tax on your sales — now auto-filled from GSTR-1, GSTR-1A or IFF and locked.
- Input tax credit — guided by your GSTR-2B for the month.
- Reverse-charge tax on purchases where you pay instead of the supplier.
- Payment — from your credit ledger first, then cash.
Due dates
- Monthly filers: the 20th of the next month.
- QRMP filers: the 22nd or 24th of the month after the quarter, depending on the state — with tax paid monthly through PMT-06 by the 25th.
What the lock means for you
If a sale was reported wrongly in GSTR-1, you can no longer simply change the figure in GSTR-3B. Correct it in GSTR-1A before filing GSTR-3B, or through amendments later. The practical result: sales data must be right before the 11th.
Time limit
Returns can no longer be filed after three years from their due date — old gaps can’t be closed later.
Key takeaways
- GSTR-3B is where tax is paid — due on the 20th (monthly).
- Tax liability now comes from GSTR-1 and can’t be edited in 3B.
- Returns older than three years can no longer be filed.
Common questions
What is the interest on late GST payment?
18% a year on the tax paid late, calculated on the cash portion. Wrongly claimed and used credit attracts 24%.
Can I file GSTR-3B before GSTR-1?
GSTR-3B now depends on the liability auto-filled from GSTR-1, so file GSTR-1 first.
Related
General information, reviewed on 3 October 2026 — not advice for your specific case. GST rules, forms and due dates change; talk to us before acting.