This book is the definitive single-volume reference for the transition from the Income-tax Act 1961 to the Income-tax Act 2025, updated to the Finance Act 2026. Spanning 1,800+ pages across four Divisions, it delivers a provision-by-provision comparative commentary across all 20 subject-matter areas, a complete TDS/TCS rate reckoner, and the full body of CBDT circulars and notifications from 1961 through February 2026—all mapped to ITA 2025 sections. It further includes a century-spanning digest of landmark Supreme Court and High Court rulings from 1922 through February 2026, dual-indexed by section and subject under the new statute. Designed for Chartered Accountants, Corporate Tax Teams, Advocates, Transfer Pricing Specialists, and Income Tax Officers, it is the only reference that resolves the section-numbering discontinuity between the two Acts and makes the entire legacy body of judicial and administrative guidance immediately accessible under the ITA 2025.