GSTR-1 and GSTR-3B: the difference and why they must match

Updated 02-10-2026

GSTR-1 lists your sales invoice by invoice and is due on the 11th. GSTR-3B is the summary return in which you pay the tax, after input tax credit, and is due on the 20th. As of October 2026 the sales tax in GSTR-3B is filled from GSTR-1 and cannot be edited, so GSTR-1 must be right first.

The two returns side by side

	GSTR-1	GSTR-3B
What it is	A statement of your sales	A summary return with payment
Detail	Invoice by invoice for business customers; summary for consumers	Totals only
Covers	Sales, credit and debit notes, exports, advances, HSN summary	Tax on sales, input tax credit, tax under reverse charge, net tax paid
Payment	None	Tax paid in cash or by credit
Due, monthly filers	11th of the next month	20th of the next month
Due, QRMP filers	13th after the quarter	22nd or 24th after the quarter
Who uses it	Your customers, whose GSTR-2B is built from it	The government, as your self-assessed tax

All dates for the year are on the GST due dates page.

How they connect

Think of the month as a chain:

You issue invoices and report them in GSTR-1 by the 11th.
Your suppliers do the same, and their invoices reach your Invoice Management System and then your GSTR-2B on the 14th.
The portal prepares your GSTR-3B: tax on sales from your GSTR-1, and input tax credit from your GSTR-2B.
You check it, pay the balance and file by the 20th.

What changed, as of October 2026

The sales side of GSTR-3B is locked. From the July 2025 tax period, the tax liability filled in from GSTR-1, GSTR-1A and the IFF cannot be edited in GSTR-3B.
Corrections go through GSTR-1A. After filing GSTR-1 and before filing GSTR-3B, you can add a missed invoice or correct one for the same period.
Credit is decided in the IMS. You accept, reject or keep pending each supplier invoice, and what you accept becomes your GSTR-2B.
Old returns close after three years. A return cannot be filed more than three years after its due date.

The practical meaning is simple. A mistake in GSTR-1 is now a mistake in the tax you pay, so the checking has to happen before the 11th, not on the 20th.

A check before you file GSTR-1

Every invoice of the month is issued, not left as a draft.
Credit notes for returns and rate differences are raised and dated in the month.
Each business customer’s GSTIN is correct. Try the GSTIN checker.
The place of supply is right, so CGST and SGST or IGST is right.
HSN codes have the number of digits your turnover requires.
The total agrees with the sales in your books for the month.

When the two still differ

Compare three numbers for the period: taxable sales in your books, in GSTR-1 and in GSTR-3B. If books and GSTR-1 differ, a document was added or changed after filing. If GSTR-1 and GSTR-3B differ for an older period, the difference was usually adjusted by hand in a later month; write down where, because your annual return will ask.

Questions

Which is filed first, GSTR-1 or GSTR-3B?

GSTR-1. The portal does not let you file GSTR-3B for a period until GSTR-1 for that period is filed, because the tax on your sales in GSTR-3B is taken from it.

Do I pay tax in GSTR-1?

No. GSTR-1 is a statement of your sales with no payment. The tax is paid when you file GSTR-3B, after setting off your input tax credit.

What if I find a mistake in GSTR-1 after filing it?

If you have not yet filed GSTR-3B for that period, correct it through GSTR-1A. If you have, show the amendment in the next period's GSTR-1.

Why do my GSTR-1 and GSTR-3B not match?

The usual causes are invoices added to the books after GSTR-1 was filed, credit notes reported in one and not the other, advances, and amendments of earlier periods. Since the July 2025 period the portal fills GSTR-3B from GSTR-1, which removes most of these differences.

Do quarterly filers file both?

Yes. Under the QRMP scheme both are filed once a quarter, GSTR-1 by the 13th and GSTR-3B by the 22nd or 24th of the month after the quarter, with tax paid monthly through PMT-06.