Income-tax Act 2025: old-to-new section number mapping (quick reference)

If you have used the Income-tax Act, 1961 for years, the 2025 Act's renumbering is the single most disorienting part of the transition. Nothing you rely on has been taken away — but almost everything has moved. This is a quick reference for the sections people actually look up.

Two things to keep straight before you use it:

1. The mapping does not change your tax. The 2025 Act is a re-codification: same rates, same deductions, cleaner drafting and new numbers.
2. Which Act applies depends on the year the income was earned, not when you file. FY 2025-26 (AY 2026-27) is still the 1961 Act. From 1 April 2026 onwards, the 2025 Act. See our full comparison of the two Acts.

Basics and the tax year

The single "tax year" replaces both the previous year and the assessment year — and for FY 2026-27 the two systems overlap. See tax year vs assessment year vs previous year.

Deductions, rebate and relief

Note the trap here: s.87A becomes s.156, and s.157 is the old s.89 (arrears relief) — two different reliefs sitting next to each other. Getting these two the wrong way round is an easy mistake.

For the full Chapter VI-A block deduction by deduction, and the point that most of it is unavailable under the default regime, see Section 80C is now Section 123.

Regimes and rates

For the slabs, the s.156 rebate and the surcharge cap that separates the two regimes at the top end, see old vs new tax regime under the Income-tax Act 2025.

Capital gains

Rates, holding periods, the surviving indexation option and the substantive change to buyback are set out in capital gains under the Income-tax Act 2025.

Business, presumptive and audit

Note that presumptive taxation (s.58) and tax audit (s.63) are different sections that are easily transposed — the thresholds and the 5% cash test for each are in presumptive taxation under Section 58.

TDS and TCS

Deductors need the table entry as well as the section, and every quarterly return form has been renumbered — see TDS under Section 393 and Income-tax Rules 2026 vs 1962.

Returns, assessment and appeals

Careful with s.156: under the 1961 Act it is the notice of demand, under the 2025 Act it is the rebate. For how to tell which Act a notice belongs to, see income tax notices under the new Act — and for matters already running, pending assessments and appeals after the repeal.

International and treaty

Residency itself stays at s.6 in both Acts. What moved for non-residents is the concessional chapter, treaty relief and withholding — see NRI taxation under the Income-tax Act 2025.

How to use this

For a past year (AY 2026-27 and earlier), keep citing the 1961 numbers — that is correct, not outdated. From Tax Year 2026-27 onwards, notices, TDS certificates and software codes will carry the new numbers. If a document about an old year quotes an old section, it is right; if a document about 2026-27 onwards still quotes old numbers, it needs updating.

This is a working reference, not the statute. For anything you are filing or relying on, confirm the section text against the Act or the department's official 1961-vs-2025 comparison utility.