Key Income Tax and GST Compliance Deadlines: September 2026 Tracker

Why Compliance Deadlines Matter: Context for September 2026

September is a significant month for statutory tax and GST compliance in India. A range of important filings, payments, and declarations for both Income Tax Act and GST regulations fall due during this period. Missing these deadlines can lead to interest, penalties, disallowance of deductions, or loss of refund opportunities. This tracker outlines all key compliance requirements for September 2026, helping businesses, professionals, and taxpayers to stay on track.

Major Income Tax Compliance Requirements

TDS/TCS Deposit and Certificates

• TDS/TCS for August 2026: Deposit by 7 September 2026 (government offices depositing without challan: same day).
• Form 127 Declarations: Upload for August 2026 by 7 September 2026.
• TDS Certificate (Form 132): Issue for TDS deducted in July 2026 by 14 September 2026.

Advance Tax & Other Important Returns

• Second Instalment of Advance Tax (FY 2026-27): Payment due by 15 September 2026.
• Client Code Modification (Form 1) by Stock Exchange: For August 2026, file by 15 September 2026.
• Non-challan TDS/TCS Statement (Form 137 by Govt Offices): For August 2026, file by 15 September 2026.
• Challan-cum-Statement (Form 141): For August 2026 TDS, file by 30 September 2026.

Income Tax Audit & Related Reports (Section 44AB & Others)

• Tax Audit Report (Section 44AB) for AY 2026-27: Due 30 September 2026 for those whose return is due by 31 October 2026 (non-corporate assessees, etc.).
• Other Audit/Report Forms Due 30 September 2026: Includes 10B/10BB, 29C, 66, 10-IL, 10-IJ, 3AC, 3AD, 3AE, 3AF, 10DA, 10CCB, etc., covering trusts, hospitals, educational institutions, special deduction claims, tonnage tax, and more.
• Income Tax Practitioner Registration Update (Form 171): Application due by 30 September 2026.

Common Deductions and Exemptions

Key sections requiring reporting/audit by the deadline include 10(4D), 10(23FF), 33AB, 33ABA, 35D, 35E, 80JJAA, 80-I, 80-IA, 80-IB, 80-IC, among others. Correct and timely filing is essential to claim related deductions.

GST Compliance Timelines for September 2026

• GST Refund Application (Form RFD-10): For eligible UIN holders, file within 2 years from the end of the relevant quarter.

Who Is Affected?

• Corporate and non-corporate assessees under income tax
• TDS and TCS deductors/collectors (businesses, government offices)
• Trusts, funds, charitable and educational institutions, hospitals
• GST registered taxpayers (all categories including QRMP, ISD, non-residents, e-commerce operators, UIN holders)
• Income-tax practitioners (for registration update duties)

Practical Implications and Action Points

• Missed deadlines attract penalty, interest, and loss of deduction/refund eligibility.
• Audit and reporting requirements are linked to claiming many common deductions and exemptions.
• Multiple forms are due (especially on 30 September 2026)—plan for document collection and professional coordination in advance.
• Keep proof of timely compliance for future audit/reference.

Worked Example: Small Company Under Tax Audit and GST

ABC Pvt Ltd (turnover Rs. 10 crore in FY 2025-26):

• Deposits TDS for August by 7 September 2026
• Pays second advance tax by 15 September 2026
• Files GSTR-1 for August by 11 September 2026
• Files GSTR-3B by 20 September 2026
• Completes tax audit by 30 September 2026

Missing any deadline can result in interest and penalty, and the tax audit delay may stop the company from claiming crucial deductions.

Tips for Staying Compliant in September 2026

• Create a digital or physical checklist with GST and Income Tax forms and deadlines
• Set reminders for all staggered due dates
• Coordinate with your CA, tax professional, and GST practitioner well in advance (especially for audit and multi-form filings)
• Double-check declarations and backup documentation