GSTR-1 and GSTR-3B due dates and changes, October 2026

GSTR-1 for September 2026 is due on 11 October, GSTR-3B on 20 October, quarterly returns by the 13th and 22nd or 24th. What changed, and the late fee.

When are GSTR-1 and GSTR-3B due in October 2026?

For a business that files every month, October 2026 holds the returns for September 2026: GSTR-1 on Sunday, 11 October 2026 and GSTR-3B on Tuesday, 20 October 2026. These are the ordinary dates, the 11th and the 20th of the month after the tax period.

For a business in the quarterly scheme, October 2026 holds the returns for the whole of July to September 2026: GSTR-1 on Tuesday, 13 October 2026, and GSTR-3B on Thursday, 22 October 2026 or Saturday, 24 October 2026, depending on the state the business is registered in.

• •GSTR-1, monthly, for September 2026: Sunday, 11 October 2026. Outward supplies for the month.
• •GSTR-3B, monthly, for September 2026: Tuesday, 20 October 2026. Summary return and tax payment for the month.
• •GSTR-1, quarterly, for July to September 2026: Tuesday, 13 October 2026. Outward supplies for the whole quarter.
• •GSTR-3B, quarterly, for July to September 2026: Thursday, 22 October 2026. Quarterly summary return.
• •GSTR-3B, quarterly, for July to September 2026: Saturday, 24 October 2026. Quarterly summary return.

Is your quarterly GSTR-3B due on the 22nd or the 24th?

It depends on the state of the registration, not on where you sell. Rule 61(1) of the CGST Rules, as substituted by Notification 82/2020-Central Tax, puts the states in two groups (Notification 84/2020-Central Tax is the one that set up the quarterly scheme itself). The quarterly GSTR-3B is due on the 22nd for a business registered in Andaman and Nicobar Islands, Andhra Pradesh, Chhattisgarh, Dadra and Nagar Haveli and Daman and Diu, Goa, Gujarat, Karnataka, Kerala, Lakshadweep, Madhya Pradesh, Maharashtra, Puducherry, Tamil Nadu and Telangana. Everywhere else it is due on the 24th.

A seller registered in two states files two returns and can have two dates: a registration in Maharashtra and one in Uttar Pradesh file on the 22nd and the 24th.

Monthly or quarterly: which dates are yours?

A registered person whose aggregate turnover in the previous financial year was up to ₹5 crore may choose the quarterly scheme (QRMP): one GSTR-1 and one GSTR-3B a quarter, tax paid every month through PMT-06, and an optional IFF for B2B invoices in the first two months of a quarter. Above ₹5 crore, every return is monthly. The choice is made on the portal, and the dates above follow from it.

Looking one month on, a quarterly filer’s October 2026 is itself a month with an IFF and a PMT-06: IFF (optional) by 13 November 2026, and PMT-06 by 25 November 2026.

What should be ready before the first due date?

Three things come from outside your books, and each has to be in hand before the return that uses it:

• •The marketplaces’ TCS. Every e-commerce operator files its GSTR-8 for September 2026 within ten days of the month’s end, under section 52(4) of the CGST Act, and the tax it collected from you appears in your TCS credit statement from it. Table 14 of your GSTR-1 should agree with that statement operator by operator, and the credit is claimed in your cash ledger under section 52(7). TCS under section 52 sets out both.
• •Your GSTR-2B for September 2026. The portal draws it up for every month from what your suppliers filed (rule 60(7) of the CGST Rules), and the input tax credit in your GSTR-3B comes from it. GSTR-2B reconciliation covers holding it against your purchase bills.
• •Every marketplace’s tax report for September 2026, downloaded after the month has closed, so that late returns and cancellations are in it. Which file to download lists the report for each.

What does it cost to file late?

A late fee for every day after the due date, charged once as central tax and once as state tax. Filed ten days late, on 30 October 2026, the GSTR-3B for September 2026 of a business with turnover up to ₹1.5 crore costs ₹500 in late fee, ₹250 under each Act, and ₹200 if the return is nil. The fee stops growing at a cap, ₹1,000 under each Act at that turnover.

GSTR-1 is charged the same way under its own notifications. Interest on tax paid late is separate from the fee and is not worked out here. The late fee guide gives each instrument and each cap.

What changed on the portal last month?

GSTN’s news page listed 3 items in September 2026, read on 25 September 2026. The third item, on 1 September, was the gross and net GST revenue for August 2026.

• •Advisory on use of version 3.3 of emSigner (19 September 2026). A DSC token issued on or after 21 September 2026 works only with version 3.3 of emSigner, the portal’s signing utility, which needs Java 1.8 and a 64-bit system. A token that already works needs no change, and 3.3 also works with older tokens. If you file with a DSC on a new or renewed token, install emSigner 3.3 from the portal’s help page before the due date, not on it. Filing with an OTP (EVC) is not what the advisory is about.
• •Enabling Filing of Appeals in Cases Involving NIL or Zero Demand Amount – reg. (7 September 2026). An appeal in Form GST APL-01 can now be filed against a demand order that shows a nil or zero demand because the tax was paid before the order. It does not touch GSTR-1 or GSTR-3B.

Which earlier changes still decide this month’s returns?

Two changes of 2025 shape every return filed now. From the May 2025 period, Table 12 has a B2B and a B2C tab, codes are picked from the portal’s HSN list, and Table 13 is mandatory (GSTN advisory of 2 May 2025); the Table 12 guide covers what the portal checks. From the July 2025 period, the liability the portal fills into Table 3 of the GSTR-3B from the GSTR-1 cannot be edited (GSTN advisory of 7 June 2025): a wrong outward figure is corrected through GSTR-1A before the 3B, not in it.

And Monday, 30 November 2026 is the last day a document of FY 2025-26 can be added to a GSTR-1 or corrected in one, under section 37(3) of the CGST Act, or earlier if the annual return for the year is filed first. A return filed after that day cannot carry it, so a missed invoice of last year belongs in the next GSTR-1 you file before it. Amending a GSTR-1 covers how.

Can these dates move?

Yes. The Commissioner can extend a due date by notification, on the GST Council’s recommendation, under sections 37(1) and 39(6) of the CGST Act, and has done so from time to time. This post gives the dates as they stood when it was written, with any extension already notified. If a date in October 2026 is extended later, the post is corrected and dated again. fynxIQ’s own reminders and calendar read the same table of dates.

The post for the month after is written on its first working day.

Where this comes from

• •GSTN, Advisory on use of version 3.3 of emSigner (19 September 2026): A DSC token issued on or after 21 September 2026 works only with version 3.3 of emSigner, the portal’s signing utility, which needs Java 1.8 and a 64-bit system. A token that already works needs no change, and 3.3 also works with older tokens.
• •GSTN, Enabling Filing of Appeals in Cases Involving NIL or Zero Demand Amount – reg. (7 September 2026): An appeal in Form GST APL-01 can now be filed against a demand order that shows a nil or zero demand because the tax was paid before the order.
• •GSTN, News and Updates: every item listed in September 2026, read on 25 September 2026.
• •Sections 37(1) and 39(6) of the CGST Act: the power to extend a due date by notification.
• •Notification 84/2020-Central Tax: the quarterly scheme and the ₹5 crore limit.
• •Rule 61(1) of the CGST Rules, substituted by Notification 82/2020-Central Tax: the two groups of states for the quarterly GSTR-3B, the 22nd and the 24th.
• •Section 52(4) and 52(7) of the CGST Act, and rule 60(7) of the CGST Rules: the operator’s GSTR-8 within ten days of the month’s end, the TCS claimed in the cash ledger, and the monthly GSTR-2B.
• •Section 37(3) of the CGST Act, as amended by the Finance Act 2022: the 30 November limit for a previous year’s documents.
• •Section 47(1) of the CGST Act and of each State Act; Notification 76/2018-Central Tax; Notification 19/2021-Central Tax: the late fee per day and its cap, in the example.
• •GSTN advisories of 2 May 2025 and 7 June 2025: Tables 12 and 13 from the May 2025 period; the GSTR-3B liability locked from the July 2025 period.
• •fynxIQ’s engine: util/period.ts, reference/late-fee.ts and validate/rules.ts: every date, the late fee and the 30 November day above are worked out by the same code the product runs.

Try it on your own figures with the free GST late fee calculator.

Which file to download, and from where: the list for each marketplace and the GST portal.

By Raunak Pathak, founder of fynxIQ, who files GST returns on it. Last updated 25 September 2026. This is general information about how GST returns work, not advice about your particular return.