Tax Year vs Assessment Year: What Changed Under the Income-tax Act, 2025?

From 1 April 2026, India’s Income-tax Act, 2025 replaces the familiar “previous year” and “assessment year” terminology with a single “tax year” concept. This is an important compliance simplification, but it is not a change in the basic timing of taxation: income earned during a tax year is still assessed after that tax year ends.

Old law — Income-tax Act, 1961

Under the 1961 Act, taxpayers routinely had to work with two year labels. The “previous year” was broadly the financial year in which income was earned, while the corresponding “assessment year” was the following year in which that income was assessed. For example, income earned during FY 2025-26 belonged to Previous Year 2025-26 and was generally associated with Assessment Year 2026-27.

New law — Income-tax Act, 2025

The 2025 Act uses “tax year” in place of “previous year” and discontinues the assessment-year label for the charging framework. The Income Tax Department explains that a tax year is a period of twelve months contained in a financial year. Accordingly, income earned during FY 2026-27 is referred to as Tax Year 2026-27.

What actually changed?

The material change is the legal vocabulary and structure used to identify the relevant year. Instead of switching between Previous Year 2026-27 and Assessment Year 2027-28 for the same stream of income, taxpayers and professionals can generally work with Tax Year 2026-27. This removes a common source of confusion in return preparation, notices, internal tax documentation and client communication.

What did NOT change?

The new terminology does not mean that income is finally assessed before the tax year closes, nor does it by itself change tax rates, the computation of total income or the underlying timing principle. The Income Tax Department has specifically clarified that income of a tax year continues to be assessed after the end of that tax year, similar to the previous-year system under the 1961 Act. The Government has also described the 2025 Act as a simplification and modernization exercise without altering the underlying tax policy.

Can a tax year be shorter than 12 months?

Yes. Where a business is newly set up during a financial year, or a new source of income comes into existence during the year, the tax year for that business or source can begin on that date and end on 31 March. The Department gives the example of a business set up on 1 December 2026: its tax year runs from 1 December 2026 to 31 March 2027.

Transition: what happens to older years?

The transition does not rewrite the tax treatment of earlier periods. The Department’s FAQ explains that section 536(3) of the Income-tax Act, 2025 provides a bridge for references to tax years beginning on 1 April 2025 or earlier: such a reference is read as the corresponding “previous year” under the old Act. Thus, a reference to Tax Year 2024-25 corresponds to Previous Year 2024-25 under the 1961 Act, which in turn corresponds to Assessment Year 2025-26.

Worked example

Assume an individual earns salary and business income between 1 April 2026 and 31 March 2027. Under the new framework, that period is Tax Year 2026-27. The income is still dealt with after the year closes in accordance with the applicable return, assessment and procedural provisions. The simplification is that professionals no longer need to describe the same income period using both “previous year 2026-27” and “assessment year 2027-28”.

Practical impact for businesses and tax teams

Businesses should update tax calendars, engagement letters, working-paper templates, return checklists, ERP tax labels and client communications to use “tax year” for periods governed by the 2025 Act. Historical records should retain their old-law PY/AY references where relevant. During the transition, teams should be especially careful when notices, litigation files or comparative schedules span periods governed by both Acts.

Effective date

The Income-tax Act, 2025 received Presidential assent on 21 August 2025 and came into force on 1 April 2026. The Income-tax Rules, 2026 were notified on 20 March 2026. The tax-year concept therefore applies to income earned from FY 2026-27 onwards.

Primary sources

Income Tax Department, “Objective and scope of the New Act” FAQs — guidance on the charging provision, Tax Year, shorter tax years and transition under section 536(3). Press Information Bureau, Ministry of Finance, 1 April 2026 — confirmation of commencement of the Income-tax Act, 2025 and the Government’s stated simplification objective.

Conclusion

For most taxpayers, “Tax Year” is best understood as a simplification of the year-label system rather than a new tax incidence. The key compliance task is to use the correct terminology for post-1 April 2026 periods while preserving accurate PY/AY references for legacy matters.

PGT & Associates assists businesses and professionals with income-tax compliance, transition issues and tax documentation. Professional advice should be obtained for facts involving multiple years or pending proceedings.

Disclaimer: This article is for general informational purposes only and does not constitute legal or tax advice. Provisions, rules, forms and administrative guidance should be checked for the relevant facts and tax year.