How We Verify Every Number

Every formula is checked against a primary source, before publishing

Before any calculator or number ships, we check it against the primary or government source — the Act itself, the government notification, the Ministry FAQ, or the relevant department's own page — not a summary of it. Where a primary source is genuinely inaccessible (some state government sites are down, host stale PDFs, or simply don't publish a clean machine-readable version), we corroborate across multiple independent secondary sources instead — and we say so, on the page, rather than presenting a secondary-sourced figure with the same confidence as a primary-verified one. You'll see this distinction called out explicitly in the trust footer of any page where it applies — for example, the payment-and-filing dates on our Professional Tax Calculator's state pages, which we corroborated via secondary sources with lower certainty than the tax slabs themselves.

"Last verified" dates, on every calculator

Every calculator and every article on this site carries a visible "last verified" date in its trust footer, alongside the specific source it was checked against. Tax rules, thresholds, and slabs change — sometimes on a predictable cycle (the Union Budget each February), sometimes not (a state amends its own Professional Tax Act on its own schedule, with no announcement most people see). A date lets you judge for yourself whether a figure is still likely to be current, instead of trusting a number with no way to check its age.

Every rule lives in exactly one file

For every calculator, every slab, threshold, cap, and rate is isolated in a single constants file — never scattered across the calculation logic or duplicated between pages. This isn't just tidy code: it means updating a rule after a Budget or an amendment is a one-line change in one place, not a hunt through the codebase hoping we find every copy. When two calculators share a genuinely identical rule — the take-home salary calculator's PF logic, for instance, reuses the exact same constants as the labour code calculator's — it's imported from the one source, not retyped, so the two can never silently drift apart.

Worked examples come from the calculator, not hand arithmetic

Every worked example on this site — the "at ₹15,00,000 CTC, your take-home is..." style walkthroughs you see throughout our articles — is computed by actually running the numbers through the calculator's own engine, the same code that runs in your browser when you use the tool, not typed out by hand. Hand-calculated examples are exactly where transcription errors creep in unnoticed; running the real engine means the worked example and the calculator can never quietly disagree with each other.

What we deliberately don't model, instead of faking precision

Some things genuinely can't be reduced to a single verified number, or would require assuming facts about your specific situation we don't have. Rather than guess and present it as exact, we say plainly what a calculator doesn't cover:

• Section 80D health insurance caps — the limit depends on your age, your family's age, and whose insurance it is (self, family, or parents, senior citizen or not). There's no single flat cap to apply, so our Old vs New Tax Regime Calculator accepts your 80D figure as trusted input rather than capping it against a guessed number.
• HRA exemption inside the tax regime calculator — HRA exemption is itself the output of a separate three-way-minimum calculation (basic salary, rent paid, and city). Rather than approximate it inline, the tax regime calculator asks for your already-worked-out HRA exemption figure, and links to the dedicated HRA Exemption Calculator to work it out properly first.
• State-by-state professional tax variation — professional tax is set independently by 13+ states and UTs, each on its own schedule. Our calculator models every state we could verify with confidence, routes a handful of states we couldn't verify to a manual-entry field rather than guessing, and we've built dedicated state pages for the largest ones rather than spreading verification thin across all of them at once.
• The EPS/EPF split within employer PF — of the employer's 12% PF contribution, a portion is diverted to the Employees' Pension Scheme (EPS) rather than your own PF account, following its own separate wage-ceiling rule. Our calculators model the combined employer PF contribution accurately but don't break out the EPS/EPF split itself, since it doesn't change what actually leaves your CTC or reaches your take-home.

Stale sources we've actually caught

This is the part most sites won't show you: specific, concrete cases where the commonly repeated figure online — sometimes even on a government site itself — was wrong or outdated, and what we found instead.

The HRA metro-city list: still shown as 4 cities, when it's now 8

HRA exemption calculations use 50% of salary for metro cities and 40% for everywhere else. For years, "metro" meant exactly four cities: Delhi, Mumbai, Kolkata, and Chennai. An amendment to the Income-tax Rules (Notification No. 22/2026, effective FY 2026-27, from 1 April 2026) added Bengaluru, Hyderabad, Pune, and Ahmedabad to that list. Most calculators we checked while building our own HRA Exemption Calculator still show the old 4-city list with no financial-year toggle at all — meaning anyone in one of the four newly added cities gets a silently wrong exemption figure. Ours models both the pre- and post-amendment rule with an explicit FY selector, since both are genuinely still relevant depending on which year you're filing for.

Karnataka professional tax: still shown as three tiers, when it's now two

The Karnataka Professional Tax (Amendment) Act, 2025, effective 1 April 2025, raised the exemption threshold from ₹15,000 to ₹25,000/month and removed the old middle slab entirely (a ₹150/month band that used to apply between ₹15,000 and ₹25,000). We found this old three-tier nil/₹150/₹200 structure still repeated across multiple tax-compliance publishers months after the amendment took effect. Our Karnataka professional tax page flags this explicitly, not as a footnote.

Section 80GG: ₹2,000/month still circulating, when it's been ₹5,000 since 2016

Section 80GG gives a rent deduction to people who don't receive HRA. The correct current cap is ₹5,000/month (₹60,000/year) — raised from ₹2,000/month by Budget 2016, nearly a decade ago. We still encountered the old ₹2,000/month figure while researching our own Section 80GG page, and flagged the discrepancy directly on it once we confirmed the current figure against a cleaner source.

₹25 lakh vs ₹20 lakh: two different gratuity figures, genuinely confused for each other

The private-sector gratuity tax-exemption limit under Section 10(10)(iii) is ₹20 lakh. A separate figure, ₹25 lakh, is the gratuity payment ceiling for central government employees under a different set of rules entirely — not a tax exemption limit, and not applicable to most private-sector employees at all. The two numbers get conflated regularly online, presumably because they're both "the gratuity ceiling" in casual phrasing. Our gratuity tax exemption page states the ₹20 lakh figure plainly and doesn't cite the ₹25 lakh figure as if it were the same thing.

incometax.gov.in's own site shows two different rebate thresholds, on two different pages

This is the most striking one: the government's own tax portal is internally inconsistent. Its general "new tax regime vs old tax regime" FAQ page still shows the pre-Budget-2025 ₹7,00,000 income threshold for the Section 87A rebate. Its current-year-specific "Salaried Individuals for AY 2026-27" page shows the correct, current ₹12,00,000 threshold. Both pages are live on incometax.gov.in at the same time. We use the current-year-specific page as authoritative for our Old vs New Tax Regime Calculator, and note this exact discrepancy in our own source documentation — because "it's on the government's website" isn't automatically the same as "it's current," even when the government's website disagrees with itself.

If you find something wrong

We'd genuinely rather hear about it than not. If a figure on this site looks stale, wrong, or inconsistent with a source you trust more, tell us via Contact — corrections like the ones above are exactly how this page's list grows. See also our Disclaimer for what these calculators are, and aren't, a substitute for.