Answer

1. F

   Facts

   For monthly filers GSTR-1 is due by the 11th of the next month and GSTR-3B, with tax payment, by the 20th. For October sales, GSTR-1 is due on 11 November and GSTR-3B on 20 November. Extensions are issued only by notification for specific months.

2. P

   Provisions and law

   • Rule 59, CGST Rules 2017Form and due date of GSTR-1; monthly filers by the 11th of the next month
   • Rule 61, CGST Rules 2017Form and manner of GSTR-3B; monthly filers by the 20th of the next month
   • Sec 39(7), CGST Act 2017Tax due must be paid by the last date for filing the return
3. A

   Analysis

   The two dates are linked. GSTR-1 must be filed first because the GSTR-3B liability is auto-filled from GSTR-1, GSTR-1A and IFF. Your buyers' GSTR-2B is generated on the 14th, so filing GSTR-1 late can also delay their credit by a month. Plan for the 11th and 20th every month and treat any extension as a bonus. For example, the September 2025 GSTR-3B date was extended to 25 October 2025 by notification, but that did not carry forward.

4. C

   Conclusion

   1. 1Send sales and purchase data to your CA by the 5th
   2. 2File GSTR-1 by the 11th and note the ARN
   3. 3Review GSTR-2B and IMS after the 14th
   4. 4Pay any cash shortfall by PMT-06 and file GSTR-3B by the 20th

Do not rely on news of an extension until a notification is issued; check the portal's news and updates.

General guidance from TaxSavvy’s library of money processes. Laws change; your Savvy confirms the answer on your exact case before anything is filed.