A tax calculator online applies the income tax slabs, deductions and rebates to your income, then shows the tax due under each regime. A good one handles:

• Slab rates for both the old and new regimes

• The standard deduction for salaried people: ₹75,000 under the new regime and ₹50,000 under the old

• The Section 87A rebate

• The 4% health and education cess

What it cannot do is check your inputs. If you forget your interest income or enter take-home pay instead of gross salary, it will still give you an answer, and that answer will be wrong.

This guide uses the slab rates announced in Budget 2025.

1. Choose the financial year and your age group. Under the old regime, senior citizens get a higher basic exemption.

2. Enter your gross salary from Form 16 or your payslips, including any bonus.

3. Add other income, such as savings and FD interest, rent, or freelance income.

4. Enter exemptions such as HRA and LTA. These count only under the old regime.

5. Enter deductions such as 80C, 80D, NPS and home loan interest.

6. Compare both results and note the difference.

7. Subtract TDS already paid, shown in Form 26AS or your AIS, to see your balance due or refund.

A tip from our advisory work: run the calculator twice. Do one run with what you have already invested and one with your planned investments. The gap shows exactly how much each extra rupee of investment saves you.

These examples assume a salaried person below 60 with no other income, and they include cess.

Example 1: ₹8 lakh salary. Under the new regime, the ₹75,000 standard deduction brings taxable income to ₹7.25 lakh. The rebate covers it fully, so the tax is nil. Under the old regime, with the ₹50,000 standard deduction and ₹1.5 lakh in 80C investments, taxable income is ₹6 lakh, and the tax is ₹33,800. The new regime saves ₹33,800.

Example 2: ₹12.75 lakh salary. Under the new regime, taxable income is exactly ₹12 lakh, so the rebate again brings the tax to nil. Under the old regime, with only the standard deduction and 80C, the tax would be ₹1,40,400. If your income is just above ₹12 lakh, marginal relief caps your tax at roughly the amount by which your income exceeds ₹12 lakh, plus cess.

Example 3: ₹20 lakh salary with heavy deductions. Under the new regime, taxable income is ₹19.25 lakh and the tax is ₹1,92,400. Under the old regime, assume this person claims:

• ₹50,000 standard deduction

• ₹1.5 lakh under 80C

• ₹75,000 under 80D (₹25,000 for the family and ₹50,000 for senior citizen parents)

• ₹50,000 in NPS under 80CCD(1B)

• ₹2 lakh in home loan interest

• An assumed HRA exemption of ₹2.4 lakh

That totals ₹7.65 lakh in deductions, leaving taxable income of ₹12.35 lakh and a tax of ₹1,90,320. Even with all these deductions, the old regime saves only ₹2,080.

For most salaried earners, the new regime now wins. The old regime pays off only with very large deductions, so always check your own numbers.

Under the old regime, these deductions make the biggest difference:

• Section 80C, up to ₹1.5 lakh: EPF, PPF, ELSS, life insurance premiums, and home loan principal. See our tax-saving investments.

• Section 80D: up to ₹25,000 for health insurance for yourself and your family, plus up to ₹50,000 more for senior citizen parents.

• Section 80CCD(1B): an extra ₹50,000 for NPS contributions.

• Section 24(b): up to ₹2 lakh of home loan interest on a self-occupied home.

• HRA exemption, if you pay rent and have receipts.

Your employer’s NPS contribution under Section 80CCD(2) is allowed under both regimes.

Even if the new regime wins for you, keep your family protected. Buy term insurance and health cover for the protection itself, not for the deduction.

In our experience, wrong results almost always come from wrong inputs. Watch for these:

• Entering take-home pay instead of gross salary

• Forgetting interest from savings accounts and FDs

• Claiming HRA while living in your own home, or without rent receipts

• Counting EPF twice, once on its own and again inside the 80C total from Form 16

• Ignoring capital gains, which are taxed at special rates that basic calculators often skip

• Using last year’s rules. From 1 April 2026, the Income-tax Act, 2025 replaced the 1961 Act, and many section numbers changed.

Tax planning works best as a habit, not a March rush. Run the numbers again:

• In April, to choose your regime and tell your employer so the right TDS is deducted each month

• After a salary hike or job change

• After buying a home or a new insurance policy

• Before submitting investment proofs, usually in December or January

• Before filing your return, to match your figures against your AIS

For goals beyond this year’s tax, use our retirement calculator alongside your tax numbers.

A tax calculator online gives you a clear answer in minutes, but only if your inputs are complete. Use gross figures, include every income source, compare both regimes, and rerun the numbers whenever your income or deductions change. For most salaried earners, the new regime now comes out ahead. Try our free tax calculator, or book a free consultation with an Excel India advisor to plan tax-smart investments and insurance.