There is a lot of confusion among the taxpayers as to which act is applicable for filing Income Tax Return in this year. Moreover the introduction of the term 'Tax Year' to replace 'Assessment Year' has added onto the confusion. 

The Income Tax Act, 1961 is effective till the year 2025-26. That is, the compliance related to the financial year 2025-26 is still the old act. The Income Tax Return has to be filed in accordance with the old act for the financial year 2025-26.

The Income Tax Act, 2025 takes effect from the year 2026-27 and the compliance related to Income from the year 2025-26 is the new act.

Earlier the term Assessment Year was used to refer to the year immediately succeeding the financial year for which return of income is required to be filed. That is for the Previous Year 2020-21, the Assessment Year was 2021-22; for FY 2021-22 the AY was 2022-23 and so on. The Income Tax Return for those financial years have to be filed within the specified due dates in those assessment years. The Assessment year for FY 2025-26 is AY 2026-27

Now the term Tax Year has effectively replaced 'Previous Year' & 'Assessment Year' to denote only the year for which the return of income is filed. That is the Tax Year for the FY 2026-27 is only 2026-27.