No other month packs in as many statutory deadlines as September. Advance tax, GST reconciliations, the tax audit, ROC filings, TDS — they all land in the same four weeks, which is exactly why we call this the mid-year compliance sprint. Get it right now, and year-end filing turns into a formality. Get it wrong, and you’re paying interest, penalties, or both. Here’s our year-end tax planning India checklist — the seven things worth your attention this month.
1. Advance Tax — Second Installment (Due 15 September)
By this date, you must have paid 45% of your full-year estimated tax liability, cumulatively. The most common mistake we see: businesses lock in their estimate using Q1 numbers and never revisit it, even as the picture changes. If your actual income runs ahead of that stale estimate, Section 234C kicks in — interest for deferring tax you should have paid on time, calculated quarter-wise regardless of what you pay later.
Example: A consumer-goods company assumed flat growth in June, paid advance tax accordingly, then saw festive-season Q3 orders spike 30%. By December, they owed a meaningful 234C interest bill on the underpaid installment — money that a mid-year revision would have avoided entirely.
Action step: Re-forecast full-year revenue using actual H1 numbers before 15 September, not your April budget.
2.Tax Audit Report — Form 3CA/3CB-3CD (Due 30 September)
If turnover exceeds ₹1 crore (₹10 crore where cash receipts and payments each stay within 5% of total transactions) or professional receipts cross ₹50 lakh, a tax audit under Section 44AB applies. This is the last mile before your ITR is due on 31 October for audited cases — miss it, and Section 271B imposes a penalty of 0.5% of turnover, capped at ₹1.5 lakh.
Example: A trading firm comfortably under the presumptive-taxation limit in April found, by August, that a run of cash sales had pushed its cash-transaction share above 5% — dragging the ₹10 crore threshold back down to ₹1 crore and triggering an audit nobody had budgeted time for.
Action step: Reconcile your cash-versus-digital transaction ratio now, before assuming you’re exempt.
3.GST Return Reconciliation (GSTR-1: 11 Sept · GSTR-3B: 20 Sept · IFF/GSTR-5 & 6: 13 Sept)
Filing on time isn’t the same as filing correctly. The real risk sits in the gap between GSTR-1 (what you reported as sales), GSTR-3B (your summary return and tax payment), and GSTR-2B (your auto-populated input tax credit, or ITC — the GST you’ve already paid on purchases and can offset against output tax). Mismatches here trigger automated notices under DRC-01B, an intimation the GST portal issues when your claimed ITC doesn’t match what your vendors have uploaded.
Example: A manufacturer lost a full month’s ITC because a key vendor filed GSTR-1 four days late — the credit simply wasn’t reflected in GSTR-2B when the manufacturer filed, and the mismatch surfaced only during the next audit.
Action step: Run a three-way reconciliation (1, 2B, 3B) before every filing, not after a notice arrives. [Internal link: GST reconciliation checklist]
4.Books Closure & Audit Readiness for FY Ending March
September is your natural mid-year checkpoint — six months into the financial year, six months before the year-end crunch. This is the ideal window to clean up ledgers, complete TDS reconciliations, and verify inventory records while there’s still runway to fix what’s broken.
Example: A services firm discovered ₹40 lakh in unreconciled vendor balances only during its statutory audit in April — balances that had been drifting since Q1 and could have been caught with a September checkpoint.
Action step: Run a mid-year trial balance review and flag every unreconciled account before it compounds.
5.ROC/MCA Compliance — AGM & DIR-3 KYC (Both due 30 September)
Companies must hold their AGM within six months of financial year-end — for a March year-end, that’s 30 September, ahead of AOC-4 (financial statements) and MGT-7 (annual return) filings. Separately, every director must complete DIR-3 KYC; miss it and the DIN is deactivated, freezing every ROC filing that needs that director’s signature, with a ₹5,000 per-DIN reactivation fee. One nuance worth knowing: recent MCA amendment rules have moved many directors to a once-every-three-years KYC cycle rather than annual filing — but if this is your first filing, or your three-year cycle falls due this year, 30 September still applies. Check individual DIN status rather than assuming.
Example: In a two-director private company, both DINs lapsed together — freezing the AGM filing itself, since neither director could digitally sign the forms.
Action step: Verify each director’s DIN status on the MCA portal this week, not the week of the deadline.
TDS/TCS Compliance Check (Deposit due 7 September for August deductions)
The recurring defaults we see: wrong section codes (194C for contractors versus 194J for professional fees — commonly swapped), deductee PAN validation failures, and late deposits attracting interest under Section 201(1A). These aren’t one-time errors; they compound every month they go uncorrected.
Example: A company classified a retainer-based consultant’s fees under 194C (contractor rate) instead of 194J (professional fees), understating TDS for months before a vendor’s Form 26AS mismatch flagged it.
Action step: Audit your last two quarters’ TDS section codes against actual contract terms, not payment descriptions.
7.Mid-Year Tax Planning & Restructuring Opportunities
With Q1 results in hand and the year-end still ahead, September is your strategic window — for capex timing, loss set-off decisions, the old-versus-new tax regime evaluation, and transfer pricing documentation for group entities.
Example: A manufacturer timed a machinery purchase for late September instead of November, securing a full year of higher depreciation claims for a marginal shift in timing.
Action step: Model your capex and regime choices now, while you still have two quarters to act on the numbers. [Internal link: advance tax calculator]
September 2026 Compliance Calendar at a Glance
| Date | Compliance | Applicable To |
| 7 Sept | TDS/TCS deposit (August deductions) | All deductors |
| 11 Sept | GSTR-1 | Regular GST taxpayers |
| 13 Sept | IFF / GSTR-5 & 6 | QRMP filers, NRIs, ISDs |
| 15 Sept | Advance tax — 2nd installment (45% cumulative) | All taxpayers with tax liability |
| 20 Sept | GSTR-3B | Regular GST taxpayers |
| 30 Sept | Tax audit report (Form 3CA/3CB-3CD) | Sec 44AB-covered businesses/professionals |
| 30 Sept | AGM + DIR-3 KYC | Private/public companies, all DIN holders |
Dates and thresholds are set by CBDT, CBIC, and MCA notifications and can shift — always verify the current position before filing.
The Bottom Line
Taken individually, these look like seven separate compliance items. Taken together, they’re a health check for the business — a moment to test whether your books, your credit claims, your governance, and your tax position can withstand scrutiny before the year-end crunch arrives. If any of the above feels less than fully under control, that’s worth a conversation now, not in March. Reach out to our team for a personalized compliance review — before the sprint becomes a scramble.
FAQ
- What is the due date for tax audit in September 2026?
For FY 2025-26 (AY 2026-27), the tax audit report is due 30 September 2026 for standard cases, with the ITR for audited entities due 31 October 2026.
- What happens if I miss the advance tax second installment deadline?
You must have paid 45% of your total estimated tax liability by 15 September; any shortfall attracts interest under Section 234C, calculated on a quarterly basis regardless of later payments.
- What is the DIR-3 KYC due date and penalty for 2026?
30 September 2026 for directors whose filing is due this cycle; missing it deactivates the DIN and attracts a ₹5,000 reactivation fee once filed late.
