Methodology & Official Sources
Exactly how each simulator turns gross pay into net pay, where every rate comes from, and how we model party promises. Last reviewed: 28 September 2026 (tax year 2026).
1. Calculation formula
Every engine implements the same pipeline. Let G be gross annual pay and D pre-tax deductions (allowances, splitting divisors, professional expenses):
Taxable base B = G − D
Income tax T = Σ over brackets (min(B, topi) − bottomi) × ratei
Net N = G − T − SSCemployee − surcharges + credits
Only income inside each band is taxed at that band’s rate — a 45% top rate never applies to the whole salary. Employee social-security charges (SSC) are computed on their own bases and caps (e.g. US Social Security wage base, German Beitragsbemessungsgrenzen, French CSG on 98.25% of pay up to caps), then credits and family divisors are applied. Results render monthly (÷12) and annually, baseline vs. selected party scenario.
2. Official sources by country (2026 statutes)
| Country | Authority & reference | Cross-check |
|---|---|---|
| United States | IRS — Publ. 15-T, Rev. Proc. brackets | IRS Withholding Estimator |
| United Kingdom | HMRC — rates & allowances | HMRC calculator, OECD |
| Canada | CRA — T1 schedules, CPP/EI | CRA payroll calculator |
| Australia | ATO — resident tax tables + Medicare | ATO calculators |
| Ireland | Revenue — credits, USC, PRSI | Revenue TaxCalc |
| New Zealand | IRD — PAYE tables, ACC | IRD calculator |
| Netherlands | Belastingdienst — box 1, arbeidskorting | Belastingdienst rekenhulp |
| Switzerland | ESTV/FTA — federal tariff; Zurich cantonal | ESTV calculator |
| Germany | BMF — tariff, Grundfreibetrag, SV | BMF Lohnrechner |
| France | DGFiP — barème, décote, CSG/CRDS | DGFiP simulateur |
| Spain | AEAT — estatal + autonómica, SS | AEAT simulador |
| Italy | MEF / Agenzia delle Entrate — IRPEF, INPS | AdE simulazioni |
| Poland | KAS — PIT 12/32%, ZUS, NFZ | KAS kalkulator |
| Turkey | GİB — tarifeler, SGK, damga vergisi | GİB hesaplayıcı |
| Japan | NTA — shotokuzei, jūminzei, shakai hoken | NTA tables, OECD |
| South Korea | NTS — geunse-sedeuk, NPS/NHIS | NTS, OECD |
| India | CBDT — new-regime slabs, cess | Income-tax calculator |
| Brazil | Receita Federal — IRPF, INSS | Receita simulador |
| Mexico | SAT — ISR tariff, IMSS | SAT calculadora |
Baseline macro-comparisons follow OECD Taxing Wages definitions (single worker, average wage, no children). National pages may model regional defaults (e.g. California, Ontario, Zurich, Catalunya) and disclose them inline.
3. How party scenarios are built
Each scenario is a documented delta on current law: rate edits, threshold/allowance shifts, SSC reforms, credits or minimum-wage interactions — sourced from manifestos and treasury costings and re-computed through the full pipeline so interactions (e.g. a higher minimum wage lifting a worker into a higher band, offset by a larger credit) are captured. Uncosted or parliament-conditional promises are labelled as such; the baseline is always current statute, never aspiration. No party receives preferential modelling.
4. Polling aggregation
Vote-intention series aggregate public polls from established houses per country (listed on each page), showing the latest rolling picture with pollster filters. Polls describe probabilities, not outcomes; seat projections and turnout effects are out of scope. Figures refresh continuously; timestamps appear above each chart.
5. Verification, limits & corrections
We cross-check every engine against the authority calculator named above; agreement within rounding is the release bar. Known simplifications (thin regional modelling, special regimes, expatriate rules, benefits-in-kind) are disclosed per page. Outputs are educational simulations — not tax, legal or investment advice. Report discrepancies via Contact with country, inputs and the official reference; verified statutory fixes ship within 72 hours and are logged here with the revision date.