GSTR-1 Is No Longer Just a Statement
GSTR-1 used to be a statement of outward supplies that fed your customers’ input credit, while your own liability was declared separately in GSTR-3B. That separation has gone. Since the July 2025 tax period the outward liability in GSTR-3B is auto-populated from GSTR-1 and is non-editable on the portal. Whatever you report in GSTR-1 is what you pay. That makes accuracy at the GSTR-1 stage the whole game.
Due dates
Filer | Return | Due |
Monthly | GSTR-1 | 11th of the following month |
QRMP | IFF, optional, first two months | 13th of the following month |
QRMP | GSTR-1, quarterly | 13th of the month after the quarter |
What goes in
Invoice-level detail of outward supplies for the period:
B2B invoices, invoice by invoice
B2C large inter-state invoices above the prescribed value, invoice by invoice
B2C small supplies, summarised
Exports and supplies to SEZ
Credit notes and debit notes
Advances received and adjusted
Nil-rated, exempt and non-GST supplies
Table 12, the HSN or SAC summary, now with separate B2B and B2C tabs and dropdown-only code selection
Table 13, the document series summary
See our article on HSN and SAC codes for the digit requirements and the Phase 3 dropdown rule.
The process
Reconcile the sales register first. Every invoice, once, with the correct value, rate, place of supply and HSN or SAC
Prepare the data, from your accounting system or the offline utility
Upload and verify the summary against your register before submitting
File with a digital signature or EVC
Check Table 12 and 13 have populated and validated
Correcting an error: GSTR-1A
An amendment facility, Form GSTR-1A, sits between GSTR-1 and GSTR-3B for the same tax period. It lets you add or correct outward records after GSTR-1 is filed and before GSTR-3B is filed.
Two features decide how useful it is:
The window closes when you file GSTR-3B. File GSTR-3B on the 17th and GSTR-1A shuts on the 17th, three days before the statutory due date. The window is yours to lose.
Sources report only one correction per tax period through GSTR-1A. Verify this for your situation, because it means the amendment has to be right.
If an error is discovered after GSTR-3B is filed, the fix moves to an amendment in a later period’s GSTR-1, with the consequences that carries for the customer’s credit and for your own reconciliation.
The errors that now cost more
A duplicate invoice. Previously an irritation. Now it inflates your locked liability.
A missed invoice. Understates liability, and the customer gets no credit.
Wrong place of supply. CGST and SGST where IGST was due, or the reverse. Correcting a head is harder than correcting a value.
Credit note in the wrong period.
Wrong HSN or SAC, which since Phase 3 may stop you filing at all if the code is not in the GSTN master.
Filing GSTR-3B before reviewing GSTR-1 output. The sequence now matters: reconcile, file GSTR-1, check the auto-populated GSTR-3B, correct through GSTR-1A if needed, then file GSTR-3B.
The three-year bar
Sources report a three-year time limit on filing past-due returns, applying across GST forms, under which the portal will not accept a return more than three years past its original due date.
For a business with old unfiled periods, that is a closing door. Deal with the backlog now.
How Northrop LLP helps
Northrop LLP reconciles the sales register to GSTR-1 before filing, uses the GSTR-1A window where a correction is needed, and sequences GSTR-1 and GSTR-3B so the locked liability is the right number.