GST returns for September 2026 are due in October: GSTR-1 on 11 October, CMP-08 on 18 October and GSTR-3B on 20 October. Quarterly (QRMP) filers have until 13 October for GSTR-1 and 22 or 24 October for GSTR-3B, depending on their state. None of these dates has been extended.
| Due | Return | Who files it |
|---|---|---|
| 11 Oct (Sun) | GSTR-1 | Monthly filers, September 2026 |
| 13 Oct (Tue) | GSTR-1 | QRMP filers, July–September 2026 |
| 18 Oct (Sun) | CMP-08 | Composition dealers, July–September 2026 |
| 20 Oct (Tue) | GSTR-3B | Monthly filers, September 2026 |
| 22 Oct (Thu) | GSTR-3B | QRMP filers in Category X states, July–September 2026 |
| 24 Oct (Sat) | GSTR-3B | QRMP filers in Category Y states, July–September 2026 |
These are the standard statutory dates, checked on 27 September 2026. CBIC can still extend a date by notification. If it does, we'll update this post. Until then, plan around the table above.
Three things to know about these dates
1. 20 October is Dussehra. GSTR-3B for monthly filers falls on a public holiday in most states. That doesn't move the date. Your accountant's office may be shut, so plan to file by Monday 19 October.
2. Two dates fall on a Sunday. GSTR-1 (11 October) and CMP-08 (18 October) are both due on a Sunday. A GST due date doesn't shift to the next working day. The portal stays open, and the late fee starts on Monday.
3. Don't count on last year's extension. In 2025, CBIC moved the September GSTR-3B from 20 to 25 October (Notification 17/2025-Central Tax, dated 18 October 2025). It gave festive holidays as the reason, and Diwali fell on 20 October that year. In 2026, Diwali is on 8 November, after every October GST date. An extension could still come, but last year's reason doesn't apply this time.
Which GSTR-3B date is yours: 20, 22 or 24 October
- Monthly filers: 20 October, for the September return.
- QRMP filers in Category X states: 22 October, for July–September. This group covers most western and southern states, such as Maharashtra, Gujarat, Karnataka, Tamil Nadu, Kerala, Telangana, Andhra Pradesh, Madhya Pradesh, Chhattisgarh and Goa.
- QRMP filers in Category Y states: 24 October, for July–September. This group covers most northern and eastern states, such as Delhi, Uttar Pradesh, Punjab, Haryana, Rajasthan, Bihar, West Bengal, Odisha, Jharkhand and the North-East.
Your state of registration decides the date, not where you sell. If you're not sure which group you're in, check the due date shown on your GSTR-3B tile on the GST portal.
What it costs if you miss one
Two separate charges apply, and they add up.
Late fee (Section 47). It's charged for each day after the due date and split equally between CGST and SGST. The same rates apply to GSTR-1 and GSTR-3B:
| Your situation | Per day | Maximum per return |
|---|---|---|
| Nil return | ₹20 | ₹500 |
| Turnover up to ₹1.5 crore | ₹50 | ₹2,000 |
| Turnover ₹1.5 crore to ₹5 crore | ₹50 | ₹5,000 |
| Turnover above ₹5 crore | ₹50 | ₹10,000 |
Turnover here means your aggregate turnover in the previous financial year.
Interest (Section 50). 18% a year, charged on the GST you pay late in cash (after using input tax credit), for each day of delay. GSTR-1 is only a statement of sales and carries no tax, so a late GSTR-1 costs you the late fee but no interest. A late GSTR-3B usually costs both.
CMP-08 works differently. A late CMP-08 means the composition tax is paid late, so 18% interest applies to it. Check the GST portal for any late fee when you file, since this calculator is built for GSTR-1, GSTR-3B and GSTR-9.
Worked example: GSTR-3B filed 10 days late
A trader with ₹2 crore turnover last year files the September GSTR-3B on 30 October instead of 20 October. They owe ₹60,000 in GST in cash after ITC.
- Days late: 10
- Late fee: ₹50 × 10 = ₹500 (₹250 CGST + ₹250 SGST). The ₹5,000 cap doesn't come into play.
- Interest: ₹60,000 × 18% × 10 ÷ 365 = ₹296
- Extra cost: ₹796, on top of the ₹60,000 tax
The same return filed as nil (no tax to pay) would cost ₹20 × 10 = ₹200, and no interest.
You can open this example in the GST Late Fee Calculator and change the dates or the tax amount to see your own figure.
Composition dealers: CMP-08 is not GSTR-4
If you're on the composition scheme, your only October date is CMP-08 on 18 October. It's the quarterly statement and tax payment for July–September. GSTR-4, the annual return, is due on 30 June after the financial year, so there's nothing to file for it now. People often mix up the two because both belong to the composition scheme.
The GST Composition Scheme Calculator works out the quarterly tax for CMP-08. Our composition scheme guide covers the rates and limits.
A short plan for October
- By 11 October: file GSTR-1 for September (monthly) so your buyers see the invoices in GSTR-2B.
- By 13 October: QRMP filers file GSTR-1 for July–September.
- By 18 October: composition dealers file CMP-08.
- By 19 October: monthly filers finish GSTR-3B, one day early because of Dussehra.
- By 22 or 24 October: QRMP filers file GSTR-3B for July–September.
Need to check a rate on an invoice before filing? The GST Calculator adds or removes GST and shows the CGST/SGST/IGST split.
Sources
- GSTR-3B: Due Date, Late Fee, Format and Rules — ClearTax
- CBIC Extends Due Date for Filing GSTR-3B for September 2025 (Notification 17/2025-CT) — Taxscan
- Diwali/Deepavali 2026 in India — timeanddate.com
This post reflects the GST due dates for October 2026 as of 27 September 2026. Check the GST portal before you file, in case CBIC issues an extension.