Income Tax Calendar 2026: 8 Key tax deadlines from August to December every taxpayer should know

The July ITR deadline has now passed, but still eligible taxpayers have several important income-tax dates to track. From advance tax payments and tax audits to ITR filing and belated return submission, the coming few months bring several critical tax compliance deadlines that taxpayers must meet.

The Income Tax Department has also clarified that AY 2026-27 relates to income earned in FY 2025-26 and is governed by the Income-tax Act, 1961, even though the new Income-tax Act, 2025, came into force on 1 April 2026.

Furthermore, the new Income Tax Act, 2025, will be applicable from the new ‘Tax Year’. This concept was introduced by the new Income Tax Act, 2025, and it completely replaces the old dual system of the ‘Previous Year’ and ‘Assessment Year’, starting from FY 2026-27.

Let us now look at important deadlines and due dates for the next few months, as it will help taxpayers in proper tax planning and meeting the remaining deadlines, thus ensuring meaningful compliance with tax authorities.

Income tax deadlines from August to December 2026

Note: The deadlines above apply to specific categories of taxpayers and may vary based on the nature of income, audit requirements and other applicable provisions. Taxpayers should verify the deadline relevant to their circumstances from the official Income Tax website before filing or making payments.

Advance tax: September and December dates matter

All eligible taxpayers who are liable to pay advance tax generally need to have paid 45% of their estimated annual tax liability by 15 September and 75% by 15 December. Furthermore, the instalments are particularly critical for taxpayers with significant income from professional fees, business, interest, capital gains or other non-salary sources. Failing to pay advance tax on time can result in taxation-related penalties, including interest and fines, under the applicable provisions.

Don't confuse belated and revised ITR deadlines

It is vital to keep in mind that the 31 December 2026 deadline is the last date to file a belated return for AY 2026-27, subject to applicable rules and assessment status. Still, the taxpayers should not confuse this with the deadline for a revised return.

In case a taxpayer has already filed a return, and later discovers mistakes or omissions, then they may be able to file a revised return until 31 March 2027, or before completion of assessment, whichever is earlier, in accordance with the applicable tax provisions.

Keep these dates on your tax calendar

In summary, with several important deadlines falling between August and December, all eligible taxpayers who are waiting to pay their taxes should first identify the category they fall under and then write down the applicable dates in a diary.

Then they should focus on collecting essentials such as PAN, Aadhaar, and a registered mobile phone, along with other relevant documents, to be ready to submit their tax returns. Achieving early compliance can help avoid last-minute errors, omissions, additional costs, and unnecessary tax-related stress.