How the Income Tax Calculator Works (FY 2025-26)
From a single gross annual income figure the calculator computes tax under both Indian regimes for FY 2025-26 (AY 2026-27) and recommends the cheaper one. The new regime subtracts a ₹75,000 standard deduction (for salaried/pension income) and applies progressive slabs — 0% up to ₹4 lakh, then 5%, 10%, 15%, 20%, 25% and 30% in ₹4-lakh bands up to ₹24 lakh and beyond — then applies the Section 87A rebate, which zeroes tax on taxable income up to ₹12 lakh with marginal relief just above it. The old regime instead subtracts a ₹50,000 standard deduction plus the deductions you enter (80C, 80D, HRA, home-loan interest, NPS), uses an age-based exempt slab and the older 0/5/20/30% rates, and gives an 87A rebate up to ₹12,500 below ₹5 lakh. Both add a 4% Health & Education cess. All math is a pure function in a small, unit-tested engine.
- New regime slabs FY 2025-26: 0/5/10/15/20/25/30% across ₹4-lakh bands
- New regime: ₹75k standard deduction + 87A rebate → tax-free to ₹12L taxable
- Old regime: ₹50k standard deduction, 80C/80D/HRA/24(b)/NPS, 87A rebate ≤ ₹5L
- Age-based old-regime exemption: ₹2.5L (<60), ₹3L (60–80), ₹5L (80+)
- 4% Health & Education cess on both; cheaper regime recommended
