A practitioner’s concordance for Sections 139 to 153 (assessment) and 147 to 151 (reassessment) — mapped to their new numbers under the Income Tax Act, 2025, for Tax Year 2026-27 filings and beyond.
What Actually Changed — And What Didn’t
The Income Tax Act, 2025, is a recodification exercise, not a rewrite of substantive assessment law. The Act now runs to 536 sections across 23 chapters, down from 819 sections and 47 chapters under the 1961 Act — achieved largely by folding provisos and explanations into the main text and removing redundant or spent provisions. For assessment and reassessment specifically, the core architecture — summary processing, scrutiny assessment, best judgment assessment, and income-escaping reassessment with a mandatory pre-notice procedure — is retained without structural change. What changes is where each provision sits.
Return Filing & Self-Assessment — Chapter XV
| Old Section (1961) | Provision | New Section (IT Act 2025) |
|---|---|---|
| 139A / 139AA | Permanent Account Number | 262 |
| 139 / 139D | Return of income | 263 |
| 139B | Scheme for submission of returns through Tax Return Preparers | 264 |
| 140 | Return by whom to be verified | 265 |
| 140A | Self-assessment | 266 |
| 140B | Tax on updated return | 267 |
Updated return window extended: the ITR-U facility (originally introduced by old Section 139(8A)) continues under new Section 263/267, with the filing window extended to 48 months from the end of the relevant tax year — up from the earlier 24-month window — giving taxpayers considerably more time to voluntarily correct omissions.
Regular Assessment Procedure — Chapter XVI
The core assessment machinery — inquiry, scrutiny, best judgment assessment, and faceless assessment — is reorganised into Chapter XVI (“Procedure for Assessment”) of the new Act, immediately following the return-filing provisions.
| Old Section (1961) | Provision | New Section (IT Act 2025) |
|---|---|---|
| 142 | Inquiry before assessment | 268 |
| 142A | Estimation of value of assets by Valuation Officer | 269 |
| 143(1) / 143(3) | Assessment — summary processing & scrutiny assessment | 270 |
| 144 | Best judgment assessment | 271 |
| 144A | Power of Joint Commissioner to issue directions in certain cases | 272 |
| 144B | Faceless Assessment | 273 |
Faceless assessment continues without interruption
The existing faceless assessment scheme continues seamlessly under the new Act — there is no re-notification or fresh scheme rollout required for pending or future faceless assessments.
Reassessment — Income Escaping Assessment
No provision has attracted more litigation in the last five years than old Section 148 and its associated machinery. This mapping is confirmed directly by the Income Tax Department’s own FAQ material on reassessment under the new Act.
| Old Section (1961) | Provision | New Section (IT Act 2025) |
|---|---|---|
| 147 | Income escaping assessment | 279 |
| 148 | Notice for reassessment | 280 |
| 148A | Inquiry / show-cause procedure before issuing notice | 281 |
| 149 | Time limit for issuing notice | 282 |
| 151 | Sanction for issuing notice (approval of specified authority) | 284 |
The 2021 reform architecture — information-led reopening, the mandatory show-cause notice and reply mechanism before any reassessment notice can issue, escaped-income-linked time limits, and prior approval of a specified authority — is preserved in substance at Sections 279 to 284. Case law developed under the old regime, including the Supreme Court’s rulings in Union of India v. Ashish Agarwal and the subsequent decision in Rajeev Bansal, continues to be persuasive authority wherever the new provision is drafted in materially the same terms.
Old Act — sequence
- Sec 148A: Show-cause notice & reply
- Sec 148A(3): Order on reply
- Sec 148: Reassessment notice
- Sec 149: Time limit (3 / 10 years)
- Sec 151: Sanction of specified authority
New Act — sequence
- Sec 281: Show-cause notice & reply
- Sec 281(3): Order on reply
- Sec 280: Reassessment notice
- Sec 282: Time limit (unchanged thresholds)
- Sec 284: Sanction of specified authority
Which Act Applies to Pending Cases?
Section 536(2)(c) — the savings clause practitioners must know
- Any assessment or reassessment proceeding already initiated under the 1961 Act before 1 April 2026 continues to be governed entirely by the 1961 Act, including all consequential steps.
- If a Section 148A(1) show-cause notice was issued before 1 April 2026, the entire sequence — the 148A(3) order and the subsequent 148 notice — is governed by the old Act, even if these later steps occur after 1 April 2026.
- The limitation period under old Section 149 continues to apply to such continuing proceedings; it is not restarted or extended by the transition to the new Act.
Example: the Assessing Officer issues a show-cause notice under old Section 148A(1) for AY 2022-23 on 20 March 2026. The order under old Section 148A(3) is passed on 15 April 2026, and the notice under old Section 148 is issued on 30 April 2026. Despite both later steps falling after the new Act’s commencement, the entire proceeding remains governed by the Income Tax Act, 1961 — old section numbers must be used throughout, not the new Sections 280/281.
Practice Notes for Drafting
Match the numbering to the date of the notice, not the date of your reply
If the original notice was issued under the old Act, keep quoting old section numbers throughout — in replies, submissions, and any writ petition — even if you are drafting after 1 April 2026.
Adopt new numbering only for genuinely new proceedings
Where the show-cause notice or assessment notice itself is issued on or after 1 April 2026, use Sections 279–284 throughout — mixing old and new numbering in the same submission signals a lack of familiarity with which regime governs.
Check whether the underlying drafting has changed, not just the number
Where a new section is drafted in materially the same terms as its old counterpart, old case law travels. Where the drafting has diverged, expect the appellate authority to read the new statute afresh rather than import old precedent automatically.
Common Questions
Do the time limits for reassessment change under the new Act?
No. The escaped-income-linked time-limit structure carried over from the 2021 reform — broadly three years, extendable up to ten years where escaped income exceeds the prescribed threshold — continues unchanged at new Section 282.
Is prior approval still required before issuing a reassessment notice?
Yes. The sanction requirement from old Section 151 continues at new Section 284, requiring approval of the specified authority before a reassessment notice can be issued.
My client’s assessment order references old Section 143(3). Is that now invalid?
No. Assessments completed, or proceedings pending, before 1 April 2026 remain governed by the 1961 Act under the savings clause at Section 536(2)(c). The old section reference remains valid for that proceeding.