Invoice Management System, GSTR-1A and the Locked GSTR-3B

The monthly GST cycle no longer ends at the 20th with a return you can type into; IMS, GSTR-1A and a locked GSTR-3B have turned it into a sequenced workflow with hard gates, and this is the day-by-day version of it.

Last verified: 5 September 2026 · Applies to: tax periods from July 2025 onward

Contents

• What actually changed
• GSTR-3B Table 3 is locked
• GSTR-1A is now the only correction route
• IMS: the four actions and when each is right
• What changed in IMS from the October 2025 tax period
• E-invoicing: the two thresholds people confuse
• The month, day by day
• Where teams get caught out
• Illustrative example
• Frequently asked questions
• How BVACA can help

What actually changed

Three things, in this order.

The Invoice Management System went live on 1 October 2024. Every inward document your suppliers file now lands on a dashboard where you accept it, reject it, hold it as pending, or do nothing. What you do there determines your GSTR-2B.

GSTR-3B Table 3 was hard-locked from the July 2025 tax period. The auto-populated outward supply values from GSTR-1, GSTR-1A and IFF are no longer editable. You cannot type over them.

GSTR-1A became the correction mechanism. If the outward figures are wrong, the fix happens in GSTR-1A, filed before the corresponding GSTR-3B, not in the 3B itself.

Put together, the return has stopped being a document you prepare at month end and become the output of decisions you make during the month. Teams that still treat the 20th as the working date find their errors after filing rather than before.

GSTR-3B Table 3 is locked

From the July 2025 tax period, the outward supply values in Table 3 of GSTR-3B are auto-populated from GSTR-1, GSTR-1A and IFF, and are non-editable.

The practical effect is a shift in where review happens. Under the old workflow a preparer could file a rough GSTR-1 and correct the summary in the 3B, so the two statements diverged routinely, and that divergence is exactly what the annual return and a later departmental audit would pick up. Locking Table 3 removes the divergence by removing the ability to create it.

It also removes the safety net. Whatever goes into GSTR-1 is what you will declare and pay on. Review moves forward, to before the GSTR-1 is filed.

GSTR-1A is now the only correction route

GSTR-1A is the amendment statement for outward supplies. Two rules govern it in practice:

1. It is filed after the GSTR-1 for the period and before the GSTR-3B for that same period.
2. Its values flow into the locked Table 3, so the corrected figure is what you pay on.

That sequence is the whole point. If you file the 3B first and then find an outward error, you have lost the correction window for that period and the fix has to be carried into a later period, which reintroduces exactly the mismatch the locking was meant to remove.

So the sequence is: GSTR-1, then check, then GSTR-1A if needed, then GSTR-3B. Not GSTR-1, GSTR-3B, and a correction later.

IMS: the four actions and when each is right

IMS is formally optional. That word does more damage than any other in this area, because inaction is not neutral. If you take no action on a record, it is treated as accepted when GSTR-2B is generated. Doing nothing is a decision to claim the credit.

Pending is not indefinite. A record held as pending can only be actioned within the input tax credit time limit under CGST s.16(4). Park an invoice long enough and the ability to claim it lapses while it is sitting on the dashboard looking like an open item. Age your pending list monthly.

Reject is not a dispute-resolution tool. It removes a record from your GSTR-2B but changes nothing about what your supplier declared. If the document is genuinely yours and merely wrong, the fix is the supplier's amendment through their GSTR-1A. Rejecting first and telling the supplier later is how a genuine credit gets lost.

What changed in IMS from the October 2025 tax period

Two changes, both aimed at credit notes.

"Pending" was extended to credit notes and certain amendments. Previously a credit note had to be accepted or rejected in the month it appeared. Now it can be held, which matters when the commercial position on a return or a rate adjustment has not settled.

A declared-ITC-reversal facility was added. When you accept a credit note, you can now declare the amount of input tax credit you are reversing against it, rather than the system assuming the full note value reverses. This is the change that matters most to businesses with high credit note volumes, because the two figures genuinely differ where the original credit was partly reversed already, was claimed proportionately, or related to a supply used partly for exempt output.

The credit note handling is where most reconciliation differences now originate. Build a monthly credit note register and reconcile it to the IMS credit note list before you act on either.

E-invoicing: the two thresholds people confuse

E-invoicing feeds the whole chain, and two separate thresholds get merged in most people's heads.

Threshold one: who must e-invoice. Aggregate annual turnover of ₹5 crore, unchanged since 1 August 2023 under Notification 10/2023-Central Tax. The test is whether AATO crossed ₹5 crore in any financial year from 2017-18 onward. The obligation is sticky: once you are in, a later fall in turnover does not take you out. It covers B2B, B2G, exports, SEZ supplies and deemed exports. B2C is excluded.

Threshold two: the 30-day reporting limit. A document must be reported to the Invoice Registration Portal within 30 days of its date only where AATO is ₹10 crore or more, and that has applied from 1 April 2025.

So a business in the ₹5 crore to ₹10 crore band must e-invoice but has no 30-day hard stop. That does not make late reporting safe: without an IRN the document never reaches your customer's IMS dashboard or their GSTR-2B, so the commercial pressure arrives well before any compliance consequence.

The month, day by day

This is the calendar for a monthly filer. Adjust the closing dates for QRMP, where GSTR-3B is due on the 22nd for Category X states and the 24th for Category Y states.

GSTR-2B is generated on the 14th of the following month (for a February tax period, GSTR-2B lands on 14 March). The IMS action cut-off is the end of 13 March — anything left at "no action" when the generator runs becomes deemed accepted. Treat 13th as the internal deadline, not the 14th.

IFF due dates for a QRMP filer: the 13th of the month after each of the first two months of the quarter. For the January-March quarter, that is 13 February (for January invoices) and 13 March (for February invoices); the March invoices go into the quarterly GSTR-1 due 13 April.

Where teams get caught out

Nobody owns the IMS dashboard. It sits between accounts payable, who hold the invoices, and the GST preparer, who holds the portal. Assign it to one named person with a daily slot.

IMS actions are taken after GSTR-2B has generated. By then the credit position for the month is fixed. Changing actions afterwards may require a recomputation, which is a step, not an automatic effect.

GSTR-2B can be recomputed via a dedicated IMS action any time between the 14th and the filing of GSTR-3B for that period, so a late-arriving invoice can still be actioned and pulled in. What cannot be recomputed is a 2B that has already fed a filed 3B — corrections then move to the next month.

GSTR-1A is skipped because "it will wash out next month". It will not wash out. It will show up as a GSTR-1 to GSTR-3B difference in the GSTR-9 and GSTR-9C guide reconciliation, and it is one of the first things a reviewing officer compares.

Pending is used as a filing cabinet. Pending records lapse against the s.16(4) limit. A pending list that only grows is a credit write-off in slow motion.

Rate masters were never updated after September 2025. If your outward rates are wrong at source, the locked Table 3 now propagates the error straight into the payment. See the post-September-2025 rate structure.

Illustrative example

Illustrative example. A manufacturer with ₹40 crore turnover files monthly. In one month it receives 620 inward documents. On the 13th, the position is 540 accepted, 22 rejected as duplicates or wrong-GSTIN, 31 pending, and 27 still at "no action" because two suppliers uploaded on the 13th and nobody looked again.

Those 27 are treated as accepted at GSTR-2B generation on the 14th. Fourteen are genuine; nine are duplicates of invoices already accepted, and four relate to a cancelled order. That is 13 documents of credit taken that should not have been, found only at the next reconciliation and reversed with interest. The fix is a cut-off, not more effort: the dashboard is worked to zero "no action" on the 13th, and anything later is handled next cycle as Pending. Figures here are illustrative and are not a client matter.

Frequently asked questions

Is IMS mandatory under GST?

IMS is formally optional, but the consequence of not using it is not neutral. Records on which you take no action are treated as accepted when GSTR-2B is generated, so ignoring the dashboard means claiming whatever your suppliers filed, including duplicates and documents that are not yours. In practice it has to be worked every month.

Can I still edit Table 3 of GSTR-3B?

No. From the July 2025 tax period the outward supply values in Table 3 are auto-populated from GSTR-1, GSTR-1A and IFF and are non-editable. If the figures are wrong, the correction is made by filing GSTR-1A for that period before the corresponding GSTR-3B, so that the amended value flows into the locked table.

When do I file GSTR-1A?

After the GSTR-1 for the tax period and before the GSTR-3B for the same period. That sequence is what allows the corrected outward figure to reach the locked Table 3. Once the GSTR-3B is filed, the correction window for that period is gone and the difference has to be carried into a later period.

What does "Pending" do in IMS, and how long can I leave a record there?

Pending holds a record out of the current month's GSTR-2B and carries it forward, which suits goods in transit or a disputed invoice. It is not open-ended: a pending record can only be actioned within the input tax credit time limit under CGST s.16(4). From the October 2025 tax period, Pending also became available for credit notes and certain amendments.

My turnover is ₹6 crore. Do I have to e-invoice, and do I have 30 days?

You must e-invoice, because the threshold is ₹5 crore aggregate annual turnover, tested against any financial year from 2017-18 onward. You do not have a 30-day reporting limit: that applies only at ₹10 crore or above, from 1 April 2025. Note that the e-invoicing obligation is sticky and does not lapse if turnover later falls.

What happens if I accept a credit note but only part of the credit was ever claimed?

From the October 2025 tax period you can declare the amount of input tax credit you are actually reversing when you accept a credit note, instead of the system assuming the full note value. This matters where the original credit was partly reversed, claimed proportionately, or related to a supply used partly for exempt output.

How BVACA can help

The change here is operational rather than legal, so the help that matters is process design and then someone running it on the calendar. We set the monthly cycle up as a dated workflow with named owners, define the IMS cut-off and the escalation route for records that arrive after it, build the purchase register to GSTR-2B and credit note reconciliations so differences are found before the 3B rather than at the annual return, and review the outward data at the point it still can be corrected. Where the finance team is small, our outsourced finance and accounting team runs the cycle end to end alongside monthly GST compliance and reconciliation. If you are also carrying older unfiled periods, read the three-year bar on filing old returns first, because that one has a deadline you cannot recover from.

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Author box: CA Vijender Singh Bachhal, Managing Partner, Bachhal Vijender & Associates (FRN 028355N), Panchkula. About the firm

Disclaimer: This article is general information current as at 5 September 2026, not advice for a specific situation. Tax and corporate law in India changed materially on 1 April 2026; verify the position before acting. Illustrative examples are not client matters.