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University · Reference · From 1 Apr 2026

Tax Year Converter.

The Income Tax Act 2025 retires sixty years of previous-year / assessment-year vocabulary: from tax year 2026-27 there is one twelve-month tax year and no AY at all. Pick any FY or AY and see what it is called under both Acts, when its return falls due, and which side of the boundary it sits on.

Pick the year you have.
I am starting from…
Financial / previous year
The transition boundary, plainly.
FY 2025-26Last year under the Income-tax Act, 1961. Previous year 2025-26, assessed in AY 2026-27 — the last assessment year that will ever exist. Returns filed in 2026 on the old forms.
Tax year 2026-27First year under the Income Tax Act, 2025 (income from 1 April 2026). No previous year, no assessment year — one tax year, defined in Sec 3.
FY 2027-28The period in which tax year 2026-27 returns are filed. It is NOT "AY 2027-28" — that label never comes into existence. Sec 263(1) fixes the due dates as calendar dates in this succeeding financial year.
Open old-year mattersAssessments, appeals and rectifications for AY 2026-27 and earlier continue under the 1961 Act (Sec 536 savings), keeping the PY/AY vocabulary for years to come.
Why it matters

The first visible transition error is terminology.

Engagement letters, audit reports, board minutes and notices will mix both vocabularies for years — old-year proceedings speak PY/AY while new-year work speaks tax year. Deliverables that use the wrong one read as drafted by someone who has not opened the new Act.

Keep going

The rest of the transition franchise.

Section mapper (1961 → 2025)Form converter (old → new)

Re-papering the practice for the new Act? Start from the firm transition checklist.

How "tax year" replaces previous year and assessment year

The Income-tax Act 1961 ran on two clocks: the previous year (when income was earned) and the assessment year (the following year, when it was assessed and the return filed). Section 3 of the Income Tax Act 2025 collapses both into a single "tax year" — twelve months from 1 April to 31 March — effective for income earned from 1 April 2026, i.e. tax year 2026-27 onwards.

The return is still physically filed in the following financial year; what disappears is the label. Section 263(1) of the new Act fixes due dates in a table as calendar dates falling in the financial year succeeding the relevant tax year — 31 July for most non-audit filers and 31 October for audit cases — without ever calling that period an assessment year.

The boundary is sharp: FY 2025-26 is the last 1961-Act year, assessed in AY 2026-27 — the last assessment year that will ever exist. Everything for that year and earlier (returns, assessments, appeals, rectifications) continues under the repealed Act through the Sec 536 savings clause, so both vocabularies run in parallel in practice files for years.

Worked example — income earned in FY 2026-27

A partnership firm (tax audit applicable) earns income between 1 April 2026 and 31 March 2027 and wants to know what to call the year and when its return falls due.

Inputs
Income earned1 Apr 2026 – 31 Mar 2027
Old-Act habitPY 2026-27, "AY 2027-28"
New-Act termTax year 2026-27 — nothing else
Governing lawIncome Tax Act, 2025
Output
Tax audit report (Form 26)Due 30 September 2027
Return due (audit case)31 October 2027 — Sec 263(1) table
What "2027-28" isJust the financial year the return is filed in — no AY label
The dates land where the old AY habit expects them — in the year after the income — but the statute now expresses them as dates in the financial year succeeding the tax year. Writing "AY 2027-28" in a deliverable for this year cites a concept the governing Act does not contain.

Common mistakes

Writing "AY 2027-28" for tax year 2026-27 income
Assessment years end with AY 2026-27. Income earned from 1 April 2026 has only a tax year; the return-filing period never gets an AY label. Software dropdowns and letter templates that auto-generate "AY" for new years need fixing.
Converting old years to the new vocabulary
FY 2025-26 and earlier remain 1961-Act years under the Sec 536 savings — their files, notices and appeals keep the PY/AY vocabulary and the old section numbers. Restating them as "tax years" is as wrong as the reverse error.
Assuming the filing calendar moved
The due-date rhythm is broadly unchanged — 31 July and 31 October in the year after the income, with the audit report at 30 September. What changed is how the statute names the period. Verify category-specific dates each season, as notifications and Finance Act changes can shift them.
Misreading the boundary at 1 April 2026
The boundary follows the year the income was earned, not the filing date. A return filed in July 2026 for FY 2025-26 is a 1961-Act filing (AY 2026-27, old forms); TDS on a payment made in April 2026 is already 2025-Act work.

Frequently asked questions

What is a tax year under the Income Tax Act 2025?+
Section 3 defines the tax year as the twelve months from 1 April to 31 March. It is the single unit for both earning and assessing income, replacing the previous-year / assessment-year pair of the 1961 Act, effective from tax year 2026-27.
What is the last assessment year?+
AY 2026-27 — it assesses income of FY 2025-26, the final year governed by the Income-tax Act 1961. From income of FY 2026-27 onwards there is only the tax year; no AY 2027-28 ever comes into existence.
When is the return for tax year 2026-27 due?+
On the dates in the Sec 263(1) table, which fall in the financial year succeeding the tax year: 31 July 2027 for most non-audit filers and 31 October 2027 for audit cases (with the tax audit report due 30 September 2027). Confirm the current season's notified dates on incometax.gov.in.
Do old assessment years continue to exist after April 2026?+
Yes. Proceedings for AY 2026-27 and earlier — assessments, reassessments, appeals, rectifications — continue under the repealed 1961 Act through Section 536(2) of the 2025 Act, keeping the old vocabulary and section numbers, potentially for many years.
Is "financial year" still used under the new Act?+
Yes — the financial year remains the general 1 April – 31 March period (returns for a tax year are due in the succeeding financial year). What disappears is the assessment year as a named concept, and "previous year" is subsumed into the tax year itself.

Authoritative sources

Income Tax Act 2025 (Secs 3, 263, 536) — CBDT / e-filing portal — Section 3 (tax year), the Section 263(1) due-date table and the Section 536 repeal-and-savings clause are the governing provisions. Verified against the CBDT transition material and published analyses as of 29 July 2026.
Always confirm against the latest version of the source. Regulations evolve and amendments are common.
Related calculators
Income Tax Act 2025 section mapper →Form converter (old → new numbers) →Income tax calculator →Firm transition checklist →
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Last reviewed: 2026-07-29 · For informational purposes only — not professional advice.