How Income Tax Calculation Works in India (New vs Old Regime)
Comprehensive guide to computing taxable income, standard deduction rules, Section 115BAC slabs for FY 2025-26 and FY 2024-25, Section 87A rebate, and the breakeven deduction threshold.
1. What Does This Income Tax Calculator Do?
This calculator evaluates your annual income tax liability under both the New Tax Regime (Section 115BAC) and the Old Tax Regime side-by-side. It takes your gross annual income, automatically factors in eligible standard deductions, itemized Chapter VI-A deductions (Section 80C, 80D, 80CCD(1B)), Section 24(b) home loan interest, and House Rent Allowance (HRA) under Section 10(13A).
The calculation engine computes marginal tax across progressive slabs for your chosen financial year (FY 2025-26 or FY 2024-25), deducts statutory rebates under Section 87A, applies the mandatory 4% Health & Education Cess, and identifies the exact rupee tax savings and recommended regime for your financial profile.
2. How Taxable Income Is Computed
Tax is not levied on your gross salary. It is levied on Net Taxable Income, derived through a structured statutory formula:
Standard deduction of ₹75,000 applies to salaried taxpayers and pensioners. Itemized exemptions (80C, 80D, HRA) are disallowed.
Permits ₹50,000 standard deduction, Section 10(13A) HRA exemption, Section 80C (up to ₹1.5L), Section 80D (health insurance), and Section 24(b) home loan interest (up to ₹2L).
3. Statutory Income Tax Slabs (FY 2025-26 & FY 2024-25)
The table below reflects statutory tax slabs enacted by Parliament. The calculator above seamlessly switches between FY 2025-26 (AY 2026-27) and FY 2024-25 (AY 2025-26) rules:
| Taxable Income Slab | New Regime (Section 115BAC) | Old Regime (General Taxpayer <60) |
|---|---|---|
| Up to ₹2,50,000 | Nil (0%) | Nil (0%) |
| ₹2,50,001 to ₹3,00,000 | Nil (0%) | 5% |
| ₹3,00,001 to ₹5,00,000 | 5% (Rebate u/s 87A) | 5% (Full rebate u/s 87A) |
| ₹5,00,001 to ₹7,00,000 | 5% (Rebate u/s 87A) | 20% |
| ₹7,00,001 to ₹10,00,000 | 10% | 20% |
| ₹10,00,001 to ₹12,00,000 | 15% | 30% |
| ₹12,00,001 to ₹15,00,000 | 20% | 30% |
| Above ₹15,00,000 | 30% | 30% |
4. Section 87A Tax Rebate & Health/Education Cess
Section 87A Rebate Provisions
- • New Regime: Resident individuals with taxable income up to ₹7,00,000 receive a tax rebate up to ₹25,000, reducing tax liability to ₹0. For salaried employees claiming the ₹75,000 standard deduction, gross income up to ₹7,75,000 is completely tax-free.
- • Old Regime: Resident individuals with taxable income up to ₹5,00,000 receive a rebate up to ₹12,500, making gross income up to ₹5,50,000 tax-free after the ₹50,000 standard deduction.
4% Health & Education Cess
Under Section 115BBE and general IT Act rules, a mandatory 4% Health and Education Cess is added to the aggregate income tax (plus surcharge, where applicable).
5. Step-by-Step Illustrative Example (₹12 Lakh Gross Salary)
| Step / Component | New Regime (Sec 115BAC) | Old Regime |
|---|---|---|
| Gross Annual Salary | ₹12,00,000 | ₹12,00,000 |
| Standard Deduction | -₹75,000 | -₹50,000 |
| Chapter VI-A (80C, 80D, HRA) | ₹0 (Disallowed) | -₹2,00,000 |
| Net Taxable Income | ₹11,25,000 | ₹9,50,000 |
| Base Tax Computed | ₹68,750 | ₹1,02,500 |
| Health & Education Cess (4%) | ₹2,750 | ₹4,100 |
| Total Tax Payable | ₹71,500 | ₹1,06,600 |
6. How to Interpret the Result: The Breakeven Deduction Threshold
The breakeven deduction threshold is the exact amount of total exemptions and deductions (HRA + 80C + 80D + Home Loan Interest) you must claim for the Old Tax Regime to equal the tax liability of the New Tax Regime.
General Rule of Thumb for Indian Taxpayers:
- If your eligible deductions are below ₹3,75,000 to ₹4,25,000 per year: The New Tax Regime almost certainly yields lower tax and higher take-home pay.
- If your eligible deductions exceed ₹4,25,000 (e.g., you have high HRA exemption in a metro city + ₹1.5L 80C + ₹2L home loan interest u/s 24b): The Old Tax Regime may yield higher tax savings.
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