Income Tax Act 2025: Key Sections — Complete Old vs New Mapping Guide

The Income Tax Act, 2025 replaces the 63-year-old Income Tax Act, 1961 with effect from 1st April 2026. While the substantive tax law remains largely unchanged, the section numbers, structure, and drafting style have been completely overhauled. For Chartered Accountants, tax professionals, and taxpayers in Bhusawal (HO), Mumbai, Pune, and across India, this means that the section numbers memorised over decades now need to be re-learned.

This is Article 3 in our five-part Transition Guide series. While Article 1 covered income heads and Article 2 dealt with TDS/TCS, this article maps the key procedural and administrative sections (महत्वपूर्ण धाराएं / नवीन आयकर कलम) that form the backbone of day-to-day tax practice: definitions, return filing, assessments, penalties, appeals, and transition rules.

1. The New Act by Numbers

Before diving into the section-by-section mapping, here is a snapshot of how the Act has been compressed and modernised:

The drafting philosophy has fundamentally shifted: Explanations and provisos that used to create confusion have been integrated into the main text of the section. Tables and formulas replace verbose narrative wherever computation is involved. This makes the Act significantly more readable for practitioners and taxpayers alike.

2. Definitions — The Foundation (Sec 2)

For decades, the dual concept of "Previous Year" (the year in which income is earned) and "Assessment Year" (the year in which it is assessed) has confused taxpayers. Under ITA 2025, a single term — Tax Year — replaces both. Tax Year 2026-27 means income earned during 1 April 2026 to 31 March 2027, and the return for this year will also reference "Tax Year 2026-27" — not "AY 2027-28."

3. Residential Status (Sec 6)

The residential status provisions are one of the few areas where even the section number has not changed. The 182-day rule, the 60+365 day rule for Indian citizens, and the POEM test for determining the residence of companies all continue identically under the new Act.

4. Filing, Payment & Processing — The Core Compliance Sections

This is where practitioners will feel the most impact in daily practice. Every section number used in return filing, tax payments, and processing has changed:

4.1 Return of Income

The most frequently cited section in Indian tax law — Section 139 — is now Section 263. The due date structure is untouched: 31 July for non-audit cases, 31 October for audit cases, and 30 November for transfer pricing. The key difference is that your return for TY 2026-27 will be filed referencing "Tax Year 2026-27" instead of "AY 2027-28."

4.2 Advance Tax

4.3 Self-Assessment Tax

5. Assessments — Intimation, Scrutiny & Reassessment

The assessment framework is the most critical area for tax litigation. Here is how each type of assessment maps to the new Act:

5.1 Intimation (Processing of Returns)

Section 143(1) — the automated processing intimation that every taxpayer receives — is now Section 270. The scope of adjustments (arithmetical errors, TDS mismatches, disallowance of incorrect claims apparent from the return) remains unchanged.

5.2 Scrutiny Assessment

Scrutiny assessments under the faceless scheme continue. The notice for scrutiny will now cite Section 272 instead of Section 143(3). All procedural safeguards — opportunity of being heard, time limits for completion, and the faceless framework — carry forward.

5.3 Reassessment (Income Escaping Assessment)

6. Penalties

Under the old Act, penalty provisions were scattered across multiple sections (270A, 271, 271A through 271FAB, 272A through 272BB, etc.). The new Act consolidates all penalties into Sections 350 to 365, making it far easier to navigate. The substantive penalty rates remain the same.

7. Appeals & Dispute Resolution

7.1 Appeal to CIT (Appeals)

7.2 Revision by Commissioner

The twin conditions for revision — that the order must be both erroneous and prejudicial to the interests of revenue — continue unchanged. The vast body of judicial precedent on Section 263 of the old Act (Malabar Industrial Co. etc.) will remain relevant for interpreting Section 377 of the new Act.

7.3 Dispute Resolution Committee

8. GAAR, APAs & International Provisions

The GAAR provisions, which target impermissible avoidance arrangements, have been carried forward without modification. All existing Advance Pricing Agreements continue to bind both the taxpayer and the revenue, ensuring continuity for multinational enterprises operating in India.

9. Transition Provisions — The Bridge (Sec 536)

Section 536 is arguably the most important provision for the transition year. Its 22 sub-clauses ensure that:

• All pending proceedings under the old Act continue under old provisions
• Losses carried forward from earlier years are recognised under the new Act
• Unabsorbed depreciation carries forward seamlessly
• Registrations granted under Section 12A (charitable trusts), 80G (donation eligibility), and similar provisions are deemed to have been granted under the new Act
• Options exercised (old regime vs new regime choice) continue to apply
• Time limits that had started running under the old Act continue uninterrupted

10. Master Reference Table — Complete Key Sections Mapping

Below is the consolidated quick-reference table mapping all key sections covered in this article:

11. What Practitioners Should Do Now

As the new Act takes effect on 1 April 2026, here are immediate action items for CAs and tax professionals:

• Update your reference sheets: Replace old section numbers with new equivalents in templates, opinions, and standard letters
• Software updates: Ensure your tax software and ERPCA references are updated for new section citations
• Client communication: Inform clients that section numbers are changing but the law itself is not — reduce unnecessary alarm
• Pending proceedings: Identify all open assessments, appeals, and reassessments — these continue under old Act provisions per Sec 536
• Dual-year readiness: During 2026-27, you will file AY 2026-27 returns under old Act while also handling TY 2026-27 under new Act