Methodology

This page explains how calculators on AlfennAI are designed, where their rules come from, what they assume, how they are tested, and how errors get fixed. It applies across the site, with finance examples drawn from the salary, HRA, PF, gratuity and professional tax calculators.

1. How calculations are designed

Each calculator is a pure function: the same inputs always produce the same outputs, with no network calls, no storage and no logging. Calculations run entirely in your browser. Inputs such as salary, CTC, HRA, rent, PF amounts or tax-regime choices never leave your device.

2. How formulas are selected

Formulas follow the governing rule, not a shortcut. Examples: take-home pay is gross salary minus employee deductions minus estimated income tax; HRA exemption is the least of actual HRA, rent minus 10% of salary, and the metro/non-metro location limit; gratuity for monthly-rated employees is monthly wage ÷ 26 × 15 per qualifying year; PF contributions are wage × rate for employee and employer separately, with an optional wage ceiling.

3. How official sources are used

Finance rules are taken from authoritative publications: Income Tax Department material for slabs, rebates, standard deduction and cess; EPFO material and the Code on Social Security framework (with Ministry of Labour & Employment / Gazette notifications) for PF rates and wage ceilings; gratuity law for the 15-day rate, the "in excess of six months" rounding rule and eligibility assumptions; and state commercial-tax / profession-tax portals for state professional-tax slabs and schedules. Pages name their sources where a concrete verification record exists — for example:

• Salary Calculator — Income Tax Department slabs and rebate rules for FY 2024-25 through FY 2026-27.
• HRA Calculator — Section 10(13A) exemption structure (old regime only; no exemption under the new regime).
• PF Calculator — EPFO 12% contribution rates with a configurable wage ceiling.
• Gratuity Calculator — statutory rate, eligibility assumptions and rounding; no invented cap.
• Professional Tax Calculator — state schedules with per-state source labels and verification dates shown in the result.

These calculators are independent estimates. They are not official calculators and the site has no government affiliation.

4. How effective dates are handled

Tax calculators ask for the financial year because slabs and rebates change between years (for example, salary earned April 2026–March 2027 is FY 2026-27). Where a rule changed mid-year — such as a wage ceiling taking effect partway through a financial year — the calculator estimates one representative current period with a configurable input instead of reconstructing earlier months.

5. How assumptions are disclosed

Every finance result shows its key assumptions next to the numbers: which standard deduction was applied, that HRA exemption and detailed 80C/80D deductions are not modelled, that surcharge is excluded, that the model covers a salaried resident individual below 60, and where employer-side components are estimated rather than known. Professional tax is subtracted from take-home pay but not from taxable income in the simplified model.

6. How calculations are tested

Each finance engine has automated tests covering worked examples, boundary cases (such as the six-month gratuity rounding rule or rebate thresholds), invalid inputs, and the finance-cluster internal-link graph. Worked examples on the page are computed by the same function as the calculator, so displayed numbers cannot drift from the implementation.

7. How financial rules are re-verified

Rule data carries verification context in the codebase (for example, per-state verification dates for professional tax). When an official rule changes, the engine constants, tests and page wording are updated together. Pages show a last-verified date only where an actual verification record exists; freshness is never fabricated.

8. How users can report errors

If you find an incorrect calculation, an outdated rule, a broken link or a misleading statement, email us via the Contact page with the page URL, the inputs you used and what you expected. Correction reports are reviewed against official sources and, when confirmed, the engine, tests and wording are corrected.

9. Why results are estimates

Real payroll depends on your employer's exact salary structure, exemption claims, TDS timing and scheme treatment — details no simplified web calculator can fully reproduce. Treat every result as an estimate to sanity-check offers and payslips, and verify regulated decisions against official sources or a qualified professional. Nothing here is financial, tax or legal advice.