Income tax calendar September 2026: Advance tax, TDS/TCS and key deadlines taxpayers must know

September brings several important income-tax compliance deadlines for taxpayers, businesses and tax professionals. The second instalment of advance tax for Tax Year 2026-27 is due on September 15, 2026, while several TDS/TCS-related compliances fall due during the month. Taxpayers and professionals also need to keep track of audit reports and various prescribed forms due by September 30, 2026, particularly where the income-tax return is due on October 31.

TDS/TCS: Deadline for depositing tax deducted or collected during August 2026. For government offices, tax deducted or collected is required to be credited to the Central Government on the same day when payment is made without production of an Income-tax Challan.

Other IT Forms: Declarations received in Form No. 127 from buyers during August 2026 must be uploaded.

TDS/TCS: Deadline for issuing Form No. 132 certificates for tax deducted at source during July 2026 in the specified cases under the Income-tax Act, 2025.

Advance Tax: The second instalment of advance tax for Tax Year 2026-27 is due on September 15.

TDS/TCS: Government offices must furnish Form No. 137 where TDS/TCS for August 2026 was deposited without production of a challan.

Other IT Forms: Stock exchanges must furnish Form 1 for August 2026 in respect of transactions where client codes were modified after registration in the system.

Form 3CE: Audit report under Section 44DA for a non-resident or foreign company, where the return is due on October 31, 2026.

Form 29B: Report for computation of book profits under Section 115JB.

Form 29C: Report for computing Adjusted Total Income and Alternate Minimum Tax under Section 115JC.

Form 66: Audit report for a tonnage-tax company under Section 115VW.

Form 10-IL: Audit report for the specified fund that is the investment division of an offshore banking unit, for claiming exemption under Section 10(4D).

Form 10-IJ: Certificate issued by a Chartered Accountant for the annual statement of exempt income of a specified Category III AIF under Section 10(23FF).

Form 10CCB: Audit report for taxpayers claiming deductions under Sections 80-I, 80-IA, 80-IB or 80-IC, where applicable.

Form 10DA: Report certifying the claim for additional employee cost under Section 80JJAA.

TDS/TCS: Form No. 141, the challan-cum-statement relating to specified TDS deductions for August 2026, is also due.

With September 15 and September 30 being the key dates, taxpayers should review their advance-tax liability and ensure that applicable audit reports, certificates, statements and other forms are filed within the prescribed timelines.