GSTR-3B hard-locking and IMS: why your invoices now decide your GST
Month-end fixes in the return are gone. Liability is locked to GSTR-1, and input credit is shaped by what you accept in IMS. Here's how it works and a monthly routine that keeps you clean.
In short
- From the July 2025 tax period, the liability auto-filled in GSTR-3B from GSTR-1, IFF and GSTR-1A cannot be edited.
- Errors in outward supplies are fixed through GSTR-1A before filing GSTR-3B, or in a later GSTR-1, not in GSTR-3B itself.
- In the Invoice Management System (IMS), invoices you don't act on are treated as accepted, so their credit flows into GSTR-2B.
- As of September 2026, input tax credit in Table 4 is still editable, but hard-locking it has been widely signalled.
GSTR-3B hard-locking means the tax liability auto-filled from your GSTR-1 can no longer be edited in GSTR-3B. It applies from the July 2025 tax period. If an invoice is wrong in GSTR-1, you fix it through GSTR-1A before filing GSTR-3B, or in a later GSTR-1, not by changing the figure in 3B. On the purchase side, the Invoice Management System (IMS) lets you accept, reject or keep pending each supplier invoice, and those actions decide the input tax credit in your GSTR-2B.
The net effect is that GST is now decided by your invoices, on both sides, at the time they're issued. The month-end adjustment in the return is largely gone.
What changed, and when?
| Change | From | What it means |
|---|---|---|
| GSTR-1A introduced | 2024 | You can amend or add outward supplies after filing GSTR-1 and before filing GSTR-3B for the same period. |
| IMS launched | October 2024 | Supplier invoices appear in IMS for you to accept, reject or keep pending before GSTR-2B is generated. |
| GSTR-3B liability hard-locked | July 2025 tax period | Liability is taken from GSTR-1, IFF and GSTR-1A and cannot be edited in GSTR-3B. |
| Input tax credit (Table 4) | Signalled; not notified as of September 2026 | Credit is auto-filled from GSTR-2B and still editable, but large over-claims trigger an intimation under Rule 88D. |
Why does hard-locking matter to a manufacturer?
Under the old routine, a wrong invoice could be patched at month-end: the accountant adjusted 3B, paid the right tax and moved on. With hard-locking, the error has to be fixed where it started. Three habits now cost money:
- Invoices typed in two places. When sales bills in one system and accounts re-keys into another, GSTR-1 reflects whichever copy was uploaded, typos included.
- Late credit notes. A return or price dispute noted on paper but not raised as a credit note in the same period inflates your liability, and you can't correct it in 3B.
- Wrong GSTIN or place of supply. These decide IGST vs CGST and SGST. Once they're in GSTR-1, they flow straight into 3B.
With e-invoicing, the invoice details reported to the IRP auto-populate GSTR-1. That helps, but only if the invoice was right when it was generated.
How does the Invoice Management System (IMS) work?
Every invoice a supplier reports in their GSTR-1 or IFF appears in your IMS. For each one, you can:
- Accept it, and its credit goes into your GSTR-2B.
- Reject it, and it's left out of GSTR-2B until the supplier corrects it.
- Keep it pending, and it carries forward (within the time limits) without being counted yet.
Invoices you don't act on are treated as accepted when GSTR-2B is generated. That default is the trap: if nobody checks, wrong invoices become your credit, and wrong credit becomes a notice later.
What to check before accepting a supplier invoice
- Is there a matching purchase bill in your books, with the same invoice number, date and taxable value?
- Did the goods actually arrive? Match the bill to a goods receipt note (GRN).
- Is the tax type right: IGST for inter-state, CGST and SGST for intra-state?
- Is it a duplicate, or a debit or credit note that needs pairing with its original invoice?
A three-way match between purchase order, GRN and bill answers the first two in seconds, if your purchase records are in one system. If they live in a register, IMS review becomes a monthly scramble.
A monthly GST routine for manufacturers
This routine assumes you file monthly. Quarterly (QRMP) filers follow the same order with their own due dates.
- Every day: raise invoices, e-invoices and credit notes from the same system that holds the order and dispatch. Book purchase bills as they arrive, against the GRN.
- By the 11th: file GSTR-1 for the previous month. Reconcile its totals with your sales register first.
- Before filing GSTR-3B: fix any GSTR-1 errors through GSTR-1A. Work through IMS: accept matched invoices, reject wrong ones, and keep genuinely disputed ones pending.
- By the 20th: file GSTR-3B. Liability comes locked from GSTR-1 and GSTR-1A, and credit comes from GSTR-2B. If you claim more credit than GSTR-2B shows, have a documented reason.
- After filing: follow up with suppliers whose invoices you rejected or kept pending, so the credit comes back next month.
Hard-locking didn't add a compliance step. It removed the place where mistakes used to get fixed quietly.
Where Dravyaa fits
Dravyaa raises sales invoices, e-invoices, e-way bills and credit notes from the order and dispatch records, so the invoice that reaches GSTR-1 is the same one your sales team raised. On the purchase side, bills are booked against purchase orders and goods receipts, which turns IMS review into a comparison of two lists. Read more in our guides to GST return filing and the e-invoicing mandate.
Frequently asked questions
What is GSTR-3B hard-locking?
From the July 2025 tax period, the outward tax liability auto-filled in GSTR-3B from GSTR-1, IFF and GSTR-1A cannot be edited. Errors must be corrected through GSTR-1A before filing GSTR-3B, or in a later GSTR-1.
Is input tax credit in GSTR-3B also hard-locked?
Not as of September 2026. Input tax credit in Table 4 is auto-filled from GSTR-2B and can still be edited, but large differences trigger an intimation under Rule 88D. Hard-locking credit has been widely signalled, so check GSTN advisories for the current position.
What happens if I don't act on an invoice in IMS?
Invoices with no action are treated as accepted when GSTR-2B is generated, so their credit flows into your return. Review invoices before GSTR-2B is generated to avoid claiming credit on wrong invoices.
What is GSTR-1A?
GSTR-1A is an optional form for amending or adding outward supplies for a tax period after filing GSTR-1 and before filing GSTR-3B for that period. The changes flow into the GSTR-3B liability.
How can manufacturers avoid GSTR-1 errors?
Raise invoices, e-invoices and credit notes from the same system that holds the sales order and dispatch, instead of re-keying them into accounting software, and reconcile GSTR-1 totals with the sales register before filing.
Sources
Facts checked as of October 4, 2026. Rules change: confirm current requirements with the official source or your tax adviser.
Get GSTR-1 right at the source
See invoices, e-invoices and purchase matching in one system in a 20-minute walkthrough.