FY 2025-26 GST correction sheet for CA firms: every GSTR-1, IFF and GSTR-3B mistake each client must fix by 30 November 2026 (sections 37(3) and 39(9))
What you get: a ready-to-copy Google Sheet layout with one row per mistake you find in a GST client's FY 2025-26 GSTR-1, IFF or GSTR-3B (missed invoice, wrong GSTIN, wrong value, wrong tax head and so on). By formula it shows each row's last date to fix, "Fix by …", "Fixed", "Window closed" or "Department case: not a self-correction", and the days left. Plus a made-up example row, a plan to 30 November and a client message. Free, no sign-up.
Short answer (checked 23 Oct 2026): the CGST Act sets one outer date for correcting a financial year's returns. Under the proviso to section 37(3) (details of outward supplies, i.e. GSTR-1/IFF) and the proviso to section 39(9) (returns, i.e. GSTR-3B), no rectification is allowed after the thirtieth day of November following the end of the financial year, or the date the relevant annual return is furnished, whichever is earlier. For FY 2025-26 that is Monday 30 November 2026, or earlier if the client files its FY 2025-26 GSTR-9 before then. This is a starting point, not tax advice.
What the law and the portal say
- GSTR-1 / IFF (section 37(3)). A registered person who discovers an error or omission in the details furnished "shall ... rectify such error or omission in such manner as may be prescribed, and shall pay the tax and interest, if any, in case there is a short payment of tax". Proviso: no rectification "after the thirtieth day of November following the end of the financial year to which such details pertain, or furnishing of the relevant annual return, whichever is earlier" (CBIC section 37 page).
- GSTR-3B (section 39(9)). An omission or incorrect particulars discovered "other than as a result of scrutiny, audit, inspection or enforcement activity by the tax authorities" is rectified in a later return, "subject to payment of interest under this Act", with the same 30 November / annual return cut-off (CBIC section 39 page). The 30 November date applies from 1 October 2022 (Finance Act 2022, notified by Notification No. 18/2022-CT).
- The GST portal's own example. The GSTR-1 FAQ says rectification of invoices of the previous financial year "will not be allowed after 30th November of the following financial year", and gives the example: for FY 2022-23 the cut-off "for amendment or for adding any missed invoice" was 30-Nov-2023. Same logic: FY 2025-26 → 30-Nov-2026.
- GSTR-1A fixes the current period only. The same FAQ: GSTR-1A amends a GSTR-1 of the same tax period, opens after GSTR-1 is filed (or its due date, if later), can be filed once per period and only before that period's GSTR-3B; its changes auto-populate GSTR-3B.
- GSTR-3B liability is fixed by GSTR-1. GSTN advisories (2025) made the auto-populated liability in GSTR-3B non-editable from the July 2025 tax period; corrections go through GSTR-1A before filing GSTR-3B, or through GSTR-1/IFF of later periods. So most output-tax mistakes for FY 2025-26 are fixed in a GSTR-1 or IFF you file by 30 November 2026.
Tab "Fix": one row per mistake
| Col | Header | What goes in |
|---|---|---|
| A | Client | Client name and GSTIN |
| B | Filing pattern | Monthly or QRMP |
| C | GSTR-9 FY 2025-26 filed on | Date, or blank if not filed (filing it brings the cut-off forward) |
| D | Where the mistake is | GSTR-1, IFF or GSTR-3B, and the period (e.g. GSTR-1 Feb 2026) |
| E | Mistake | Missed invoice / wrong GSTIN / wrong taxable value / wrong rate / IGST instead of CGST+SGST (or the reverse) / credit or debit note missing / other |
| F | Found by | Own review, or Department (scrutiny, audit, inspection or enforcement) |
| G | Tax effect (₹) | Positive if tax was short paid, negative if excess |
| H | Fix route | Amendment / missed invoice in GSTR-1 or IFF of a later period, or later GSTR-3B |
| I | Fix in period | The period of the return or statement that carries the fix (e.g. GSTR-1 Oct 2026) |
| J | Fix filed on | Filing date of that return or statement |
| K | Interest | "Check" where G is positive; note what was paid. This page does not state a rate. |
| L | Last date to fix | =IF(C2="",DATE(2026,11,30),MIN(DATE(2026,11,30),C2)) |
| M | Status | =IF(LEFT(F2,4)="Dept","Department case: not a self-correction",IF(J2<>"",IF(J2<=L2,"Fixed","Filed after cut-off: check"),IF(TODAY()>L2,"Window closed","Fix by "&TEXT(L2,"d mmm yyyy")))) |
| N | Days left | =IF(LEFT(M2,6)="Fix by",L2-TODAY(),"") |
On a "Clients" tab, count open rows per client: =COUNTIFS(Fix!A:A,A2,Fix!M:M,"Fix by*"), and the short-paid tax still to fix: =SUMIFS(Fix!G:G,Fix!A:A,A2,Fix!M:M,"Fix by*",Fix!G:G,">0").
Made-up example row
| A | B | C | D | E | F | G (₹) | H | I | L | M |
|---|---|---|---|---|---|---|---|---|---|---|
| Client 1 | Monthly | GSTR-1 Feb 2026 | B2B invoice reported under wrong GSTIN | Own review | 0 | Amend in later GSTR-1 | GSTR-1 Oct 2026 | 30 Nov 2026 | Fix by 30 Nov 2026 |
Example only: the client, invoice and figures are made up for illustration.
Plan to 30 November
| When | What |
|---|---|
| Fri 23 – Sat 31 Oct | For each GST client, compare the FY 2025-26 books with GSTR-1, IFF and GSTR-3B. Add a row for every difference. Ask the client the questions below. |
| Wed 11 Nov | Monthly clients: GSTR-1 for October 2026 is due. Carry the FY 2025-26 amendments and missed invoices in it. |
| Fri 13 Nov | QRMP clients: IFF for October 2026 (optional) is due. Their next GSTR-3B (October–December quarter) falls due in January 2027, after 30 November, so plan their fixes in a statement actually filed by 30 November and check on the portal that the table you need is open. |
| Fri 20 Nov | Monthly clients: GSTR-3B for October 2026 is due. Use GSTR-1A for October first if the October GSTR-1 itself has an error. |
| Mon 30 Nov | Last date for FY 2025-26 rectification under sections 37(3) and 39(9). Do not file a client's FY 2025-26 GSTR-9 before its rows here are closed, because filing it ends the window on that date. |
Client message
"Before 30 November 2026 we can still correct mistakes in your GST returns for April 2025 – March 2026. After that date the law does not allow it. Please send, by [date]: any sales invoice, credit note or debit note of that year you think was left out, any customer who said their GSTIN or amount was wrong on our filing, and any change in the place of supply. We will add the fixes to your return for [period]."
Notes
- Section 39(9) does not cover mistakes found "as a result of scrutiny, audit, inspection or enforcement activity by the tax authorities". Mark those rows "Department" and deal with them in that proceeding.
- Credit notes and ITC have their own 30 November limits: see our section 34 credit note guide and section 16(4) ITC guide. Supplier-side ITC reversals are on the rule 37A sheet.
- Where tax was short paid, interest applies; see our section 50 interest guide.
Related guides
- GSTR-9 / 9C FY 2025-26 chase list
- IMS invoice action sheet (October 2026)
- GSTR-1 chase list before the 11th
- Three-year bar sheet for unfiled returns
- November 2026 due-date chase list
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