September 2026 Tax Compliance Calendar: GST, TDS, Advance Tax & Tax Audit

Updated 28 September 2026: CBDT extended the AY 2026–27 tax-audit report due date to 21 October and the related audited ITR due date to 21 November for persons at S. No. 2 of Explanation 2 to section 139(1). The separate transfer-pricing Form 3CEB deadline is not covered. Official Income Tax Department announcement

September is the busiest compliance month of the year for most Indian businesses. GST returns for August, the second advance-tax instalment and the AY 2026-27 tax audit report all fall in the same window. Use this calendar, then send your books to a CA before the last week of the month.

Key September 2026 dates

• 7 September 2026: GSTR-1 for August 2026 (monthly filers).

• 10 September 2026: GSTR-7 (TDS under GST) and GSTR-8 (TCS).

• 11 / 13 September 2026: GSTR-1 IFF for QRMP taxpayers (as applicable) and GSTR-6.

• 15 September 2026: Second instalment of advance tax (45% cumulative) for FY 2026-27. Also a common ESI / PF due date.

• 20 September 2026: GSTR-3B for August 2026 (monthly).

• 21 October 2026: Tax audit report for AY 2026-27 (Form 3CA/3CB with Form 3CD), extended by CBDT on 28 September.

Do not mix 21 October and 21 November

The tax audit report for the specified audited category is due on 21 October 2026. The ITR for a taxpayer who is subject to tax audit is a separate date: 21 November 2026. Transfer-pricing Form 3CEB follows the 3CEB timeline, not the ordinary section 44AB report date. Confirm the latest CBDT notification before you file; dates can be extended.

What to send your CA this week

• Trial balance, GST vs books reconciliation, and Form 26AS / AIS mismatches.

• TDS returns, MSME (section 43B(h)) ageing, cash receipts/payments above the 269ST / 269SS limits.

• Related-party ledgers and any Form 3CEB working papers.

Need the September filings done from Ahmedabad?

PGT & Associates handles GST returns, advance-tax computation and tax-audit e-filing. Call +91-87994-99189 or email info@pgtandassociates.com. Tell us your turnover and whether a tax audit already applies so we can lock a 21 October slot.