What is GSTR-3B?

GSTR-3B is the monthly summary return through which a business declares its total sales, claims input tax credit and pays the net GST due.

Unlike GSTR-1 it carries no invoice-level detail — only totals. It is due on the twentieth of the following month for monthly filers, with staggered dates of the twenty-second and twenty-fourth for QRMP filers depending on state.

Tax is actually paid here. A GSTR-1 filed without the matching GSTR-3B means the sale is declared but the tax is not paid.

Why it matters

Late filing attracts ₹50 a day, and the portal blocks GSTR-1 for the next period until the previous GSTR-3B is filed — so one missed month cascades.

The statutory position

Each figure with the provision it comes from, so it can be checked.
What	Position	Source
Due date, monthly filers	20th of the following month	Rule 61, CGST Rules 2017
Due date, QRMP filers	22nd or 24th of the month following the quarter, by state	Notification 84/2020-Central Tax
Late fee	₹50 per day, ₹20 for nil returns, subject to a turnover-based cap	Section 47 read with Notification 19/2021
Interest on late payment	18% per annum	Section 50(1), CGST Act 2017
Consequence of two consecutive defaults	E-way bill generation blocked	Rule 138E, CGST Rules 2017

Not to be confused with

These get used interchangeably, including by tools that should know better. They are different things.

GSTR-1

GSTR-1 is the invoice-level outward statement. GSTR-3B is the summary return where tax is paid. They report the same sales and are checked against each other.

GSTR-9

GSTR-9 is the annual reconciliation of everything already filed. It does not replace the monthly 3B and cannot be used to correct a year of them.

Questions people ask

Do I file if there were no sales?

Yes. A nil return is still a return, and the ₹20-a-day late fee runs on it. Returns also cannot be filed out of order, so one skipped nil month blocks every month after it.

Can I fix a mistake in a filed 3B?

Not by revising it — 3B cannot be revised. Corrections are made in a later period's return, and the adjustment is explained in the annual reconciliation.

What usually goes wrong

Skipping a nil return and blocking every subsequent period
Claiming input credit that is not in GSTR-2B
Omitting reverse charge liability, particularly commercial rent from an unregistered landlord
Paying under the wrong head — IGST where CGST and SGST were due — which needs a fresh payment and a refund claim