Understanding the Tax Year Concept in Income Tax Act 2025

What is Tax Year under the Income Tax Act 2025? Tax Year is a single 12-month period (April 1 to March 31) introduced by the Income Tax Act 2025 that consolidates the old Financial Year and Assessment Year into one concept. The return for income earned during Tax Year 2026-27 is filed after that year ends (in 2027) but carries the same Tax Year 2026-27 label, replacing the prior system where earning and assessment fell in two separately named years.

The Income Tax Act 2025 carries the most significant structural overhaul of Indian income tax law since 1961. Most of the substantive law remains unchanged (tax slabs, most due dates, deduction limits), but the architecture is reorganised, and the terminology shifts meaningfully. The FY/AY distinction that has tripped up taxpayers for decades is now replaced by a single term: Tax Year. Here is what that means in practice.

What Was Financial Year and Assessment Year?

Under the Income Tax Act 1961, income tax operated across two distinct 12-month windows:

Financial Year (FY): The year in which you earned the income. FY 2025-26 ran from April 1, 2025 to March 31, 2026. This is when your salary was credited, your business revenue accrued, and your capital gains arose.

Assessment Year (AY): The year immediately following the FY, during which you filed your return and the Income Tax Department assessed (processed) it. AY 2026-27 ran from April 1, 2026 to March 31, 2027. Your ITR for income earned in FY 2025-26 was due by July 31, 2026, which falls within AY 2026-27.

The result: you always referenced two years simultaneously. "I earned income in FY 2025-26 and am filing for AY 2026-27" was grammatically correct but practically confusing, particularly when an employer issued Form 16 under one year label while the portal asked for another. Non-specialists routinely conflated the two, leading to errors in AY selection while filing ITRs.

What Is Tax Year Under the Income Tax Act 2025?

The Income Tax Act 2025, which replaces the 1961 Act effective from April 1, 2026, introduces the term Tax Year as defined in Section 3 of the new Act: the twelve-month period of the financial year starting on 1 April (or a shorter first period for a newly set up business or new source of income). It is the same window as the old Financial Year. The return for that Tax Year is filed after the year closes.

The critical shift: the year you earn income and the year your return relates to now carry the same label. Tax Year 2026-27 covers income earned from April 1, 2026 to March 31, 2027, and the return filed for that income is also described as the Tax Year 2026-27 return. There is no separately named "Assessment Year 2027-28" under the new framework.

This brings India into alignment with how most jurisdictions worldwide refer to their tax periods. The UK's Self Assessment uses Tax Year. The US uses Tax Year. Australia uses Income Year. The FY/AY dual-label was a structural peculiarity of the 1961 Act that the 2025 Act has now corrected.

Mapping: FY/AY to Tax Year, A Practical Table

The transitional row deserves attention. Income earned in FY 2025-26 was earned under the 1961 Act. The return filed in July 2026 references AY 2026-27. Although the new Act is effective from April 1, 2026, it does not retroactively relabel prior-year returns. Your July 2026 filing will still show AY 2026-27 on the ITR form and on Form 26AS.

From FY 2026-27 onwards, the new Act applies in full. Returns for income earned April 2026 onwards will be filed under Tax Year 2026-27 terminology.

What Changes and What Stays the Same for Taxpayers

What changes:

• Terminology on ITR forms and CBDT communications: "Assessment Year" fields will transition to "Tax Year"
• Section numbering throughout the Act (covered separately below)
• The framing in CBDT circulars, notices, and assessment orders issued from April 1, 2026 onwards

What does not change:

• Due dates: ITR filing due date for salaried taxpayers (ITR 1 and ITR 2) remains July 31. Audit cases remain October 31. Belated return deadline remains December 31. One change came through the Finance Act 2026: non-audit business and professional cases now file by August 31 instead of July 31, and revised returns can be filed up to 12 months from the end of the year (March 31), with a fee if filed after 9 months.
• Tax slabs: The new and old regime slabs, surcharge thresholds, and cess rates carry over unchanged
• Deduction limits: Rs 1.5 lakh under Section 80C (now Section 123), Rs 25,000 / Rs 50,000 health insurance premium under Section 80D (now Section 126), HRA computation, all preserved
• TDS provisions: TDS rates and threshold limits continue; section references change (Section 192 is now 392, most other TDS sections sit in 393) and forms are renumbered (Form 16 becomes Form 130, Form 16A becomes Form 131)
• Penalty and interest provisions: Section 234A, 234B, 234C interest and the 234F late fee are preserved, renumbered as Sections 423, 424, 425 and 428

For the practical taxpayer, the change is primarily cosmetic in Year 1. The compliance calendar you follow today works identically under the new framework.

Section Renumbering: Where Did Your Deductions Move?

The Income Tax Act 2025 reorganises sections into a more logical structure. Practitioners and taxpayers who cite section numbers in correspondence, investment declarations, or Form 10BA must update their references. Key mappings:

Full section-wise mapping tables of the 1961 Act to the 2025 Act are published alongside the Act text, for example in the ICAI Direct Taxes Committee edition. For returns and filings under AY 2026-27 (income of FY 2025-26), the old section numbers remain operative. Transition to new section references only for transactions and filings from Tax Year 2026-27 onwards.

If you want the full picture of structural changes, read our Income Tax Act 1961 vs 2025 comparison which covers the chapter reorganisation, simplified language initiative, and changes to procedural provisions.

When Does Tax Year Apply? FY 2025-26 vs FY 2026-27

The activation boundary is April 1, 2026:

• Income earned before April 1, 2026 (FY 2025-26): Governed by the Income Tax Act 1961. Your ITR references AY 2026-27. Old section numbers apply. Form 16 for FY 2025-26 will cite old sections.

• Income earned from April 1, 2026 (Tax Year 2026-27 onwards): Governed by the Income Tax Act 2025. Returns reference Tax Year 2026-27. New section numbers apply. Employers will issue the salary TDS certificate as Form 130 (the successor to Form 16), citing new section references, from June 2027 onwards (for income earned in Tax Year 2026-27).

There is a practical overlap period. Between April 1, 2026 and July 31, 2026, you will simultaneously be filing an AY 2026-27 return (old Act, for FY 2025-26 income) while also earning income under the new Tax Year 2026-27 framework. Both systems run in parallel during this window.

CBDT is expected to issue transition guidelines addressing this overlap, particularly for advance tax computation and TDS certificate formats. Monitor official CBDT circulars for formal instructions.

For filing support or questions about which framework applies to your specific situation, our support team can walk you through the transition. Fixed-fee ITR filing plans are available at our pricing page.

Impact on ITR Forms and Filing Due Dates

CBDT will rename the ITR forms currently labelled for "Assessment Year 2027-28" to reflect "Tax Year 2026-27" once the new Act applies. The seven form types remain:

• ITR 1 (Sahaj): Resident individuals, salary + up to two house properties (as allowed from the AY 2026-27 form) + other sources, income up to Rs 50 lakh
• ITR 2: Individuals and HUFs without business income
• ITR 3: Individuals and HUFs with business or professional income
• ITR 4 (Sugam): Presumptive income under Section 58 (new numbering for 44AD, 44ADA and 44AE)
• ITR 5, ITR 6, ITR 7: Firms, companies, trusts

Check the forms notified for Tax Year 2026-27 before filing, as CBDT can revise eligibility each year.

Filing due dates under Tax Year 2026-27:

• Individuals and HUFs without business income (ITR 1 / ITR 2 type): July 31, 2027
• Business or profession without audit, and partners of non-audit firms: August 31, 2027
• Businesses requiring audit, and partners in firms requiring audit: October 31, 2027
• Belated return: December 31, 2027
• Revised return: March 31, 2028 (fee applies if filed after December 31, 2027)

These dates follow Section 263 of the Income-tax Act, 2025 as amended by the Finance Act 2026.

Sources: Income Tax Act 2025 (as enacted), CBDT press releases on Act restructuring, Section 3 of the Income Tax Act 2025 (definition of Tax Year), Ministry of Finance notifications on effective date. Section mapping references are based on the enacted text of the Income Tax Act 2025. For transactions and filings under the Income Tax Act 1961 (up to FY 2025-26), the old section numbering remains operative.

Frequently Asked Questions

Does the new Tax Year concept change my ITR for income earned in FY 2025-26?

No. Income earned from 1 April 2025 to 31 March 2026 is governed by the Income-tax Act, 1961, and its return is filed for Assessment Year 2026-27 with the old section numbers and forms, including Form 16 from employers. The Tax Year label and the new Act apply to income earned from 1 April 2026, which is Tax Year 2026-27.

When will I file the return for Tax Year 2026-27?

After the Tax Year ends. Tax Year 2026-27 runs from 1 April 2026 to 31 March 2027, and the return for that income will be filed in 2027, after the year closes, just as returns were filed in the assessment year earlier. Only the label changes: the return is described by the year in which the income was earned rather than a separate assessment year.

Is Tax Year 2026-27 the same period as FY 2026-27 and AY 2027-28?

Yes, all three refer to income earned between 1 April 2026 and 31 March 2027. Under the old system, this income would have been called FY 2026-27 income, assessed in AY 2027-28. Under the Income-tax Act, 2025, it is simply Tax Year 2026-27. When a portal or document still says AY 2027-28, it is referring to the same income.

Do advance tax dates change under the Income-tax Act, 2025?

No. For Tax Year 2026-27, advance tax still falls due in instalments of 15% by 15 June, 45% by 15 September, 75% by 15 December and 100% by 15 March, with presumptive taxpayers paying the full amount by 15 March. It applies when estimated tax after TDS is Rs 10,000 or more, and shortfall interest continues at 1% per month.

Will my old investment proofs and section references still work with my employer?

For salary paid up to March 2026, employers use the 1961 Act sections, such as 80C and 80D, and issue Form 16 for FY 2025-26. For salary from April 2026, payroll software and declarations use the new Act's section numbers and forms, although the main deduction limits, like Rs 1.5 lakh for 80C-type investments under the old regime, carry over.