The second half of the financial year is where the deadlines stack up. Between September and December 2026 a proprietor has advance tax and possibly an audit ITR to deal with; a company has all of that plus AGM, ROC filings and the GST annual return. This post lays out the whole quarter-and-a-bit month by month. Bookmark our live compliance calendar for the always-current version — dates below are as they stand today.
First, the one that cannot wait: 31 August
Before September even starts, the non-audit ITR deadline for business and professional income lands. Under the Finance Act 2026 split, ITR-1 and ITR-2 were due 31 July; ITR-3 and ITR-4 for non-audit cases are due 31 August 2026. If you run a proprietorship or practice under the section 58 presumptive scheme and have not filed yet, that is this month's job, not September's. Our ITR-3 filing service exists for exactly this crunch.
September 2026
| Date | What | Applies to |
|---|---|---|
| 15 Sep | Advance tax, second instalment (45% of the year's estimated tax, cumulative) | Everyone with tax payable above ₹10,000 — proprietors and companies alike |
| 30 Sep | Last date to hold the AGM for FY 2025-26 | Companies only |
| Through Sep | GSTR-9/9C groundwork: books-to-returns reconciliation for FY 2025-26 | GST-registered businesses above the annual return threshold |
September is also the month to get your tax audit moving if section 63 (the old 44AB) applies to you — the audit report is generally due ahead of the October return date, and auditors do not get faster as their queue grows. And if GSTR-9/9C applies, start the reconciliation now: the FY 2025-26 annual return spans the rate change of 22 September 2025, so most businesses have two rate structures inside one year. Untangling that in December is miserable; in September it is routine. See our GSTR-9/9C service if you want it off your desk.
October 2026
| Date | What | Applies to |
|---|---|---|
| 31 Oct | ITR for audit cases (tax year 2025-26) | Proprietors and companies under tax audit |
| 31 Oct | TDS returns for Q2 (Jul–Sep): salary and non-salary statements | Anyone deducting TDS — including firms paying partners under 194T |
| Within 30 days of AGM | AOC-4 (financial statements to ROC) — 30 Oct if your AGM was on 30 Sep | Companies only |
October is the heaviest month on this list for companies: audit ITR, Q2 TDS returns and AOC-4 can all land within days of each other. ROC late fees run at ₹100 per day with no upper cap, so AOC-4 is not a deadline to test.
November 2026
| Date | What | Applies to |
|---|---|---|
| Within 60 days of AGM | MGT-7 / MGT-7A (annual return to ROC) — 29 Nov if your AGM was on 30 Sep | Companies only |
| Through Nov | DPDP consent-manager obligations begin phasing in | Businesses processing personal data digitally — worth a readiness check |
November looks quiet on paper. Treat it as the buffer month: clear any GSTR-1/3B mismatches while there is still time to amend, because the hard-locked 3B regime means corrections flow through GSTR-1A, not through editing the return — we covered that shift in our GSTR-3B hard-lock explainer.
December 2026
| Date | What | Applies to |
|---|---|---|
| 15 Dec | Advance tax, third instalment (75% cumulative) | Everyone with advance tax liability |
| 31 Dec | Belated return window closes for tax year 2025-26 (section 428(b) fee applies) | Anyone who missed their ITR deadline |
| 31 Dec | GSTR-9 and GSTR-9C for FY 2025-26 | GST-registered businesses above the annual return threshold |
Two hard stops share 31 December. The belated return is the last chance to file for 2025-26 at all — after that, only a revised return of something already filed (open until 31 March 2027) or nothing. And the GST annual return lands the same day, which is why the September groundwork matters. Remember the three-year bar too: the portal now permanently blocks GST returns more than three years past due, so "later" is no longer a strategy anywhere in this calendar.
The monthly drumbeat underneath
All of the above sits on top of the routine cycle that does not pause: TDS deposit by the 7th, GSTR-1 by the 11th, GSTR-3B by the 20th, every month. If a late fee has already accrued somewhere, our GST late fee calculator will tell you the damage in thirty seconds.
How we can help
This calendar is what our retainer clients never have to think about. We run the monthly filings, the quarterly TDS returns, the ROC season and the year-end GST close for 300+ businesses on plans from ₹2,999 a month, with no lock-in. If the list above made you check a date twice, send it to us instead.
See the live, always-updated compliance calendar →
This article is general information, not tax advice. Rules and rates can change; confirm specifics for your business before acting.