Methodology & data sources
Every country’s calculator on mytakehomepay.app is checked against that country’s own reference calculator. This page lists the reference, the tolerance, how many cases the engine is locked against, and whether that lock is a live scrape of the reference or a hand-derived fixture set — so you can decide for yourself how much to trust each result.
Last verification run: 25 May 2026 (NL added) · 87 fixtures across 12 countries · questions: info@mytakehomepay.app
How verification works
Two kinds of verification run on every commit:
- Scraped snapshot. Today Germany only. A Playwright script (
pnpm verify:de) drives the BMF Lohnsteuer-Rechner headlessly for the 29 fixture inputs, writes the snapshot, and a Vitest loop replays every input through the engine and asserts the result within the published tolerance. The build fails the moment any fixture drifts. - Hand-derived fixtures.UK, US, France and Spain. The expected net for each case was computed by hand from the authority’s published bands and cross-checked against the country’s reference calculator on the day the fixture was written, then locked into the test suite. The same Vitest loop replays every commit; the build fails if the engine drifts. The roadmap is to extend the scraper pattern (
verify:<cc>) to all four so the snapshot is recomputed from the reference on a schedule, not pinned to a single point in time.
The verification table below makes the distinction explicit per country.
Per-country status
| Country | Tax year | Reference | Verification | Tolerance | Fixtures |
|---|---|---|---|---|---|
| United Kingdom | 2025/26 | HMRC Estimate your Income Tax | Hand-derived | ±£0.05 on each fixture | 23 |
| Germany | 2026 | BMF Lohn- und Einkommensteuerrechner | Scraped | ±€20 / month on net (±€240/yr); Lohnsteuer ±€240; Soli + Kirchensteuer ±€50 | 29 |
| United States | 2025 | SmartAsset state paycheck calculators | Hand-derived | ±$5 on each fixture | 10 |
| France | 2025 | URSSAF mon-entreprise | Hand-derived | ±€500 per year | 3 |
| Spain | 2025 | Cinco Días sueldo neto | Hand-derived | ±€500 per year | 2 |
| Canada | 2025 | CRA Payroll Deductions Online Calculator | Hand-derived | Engine output frozen against itself; CRA scraper deferred | 13 |
| Italy | 2025 | Agenzia delle Entrate — IRPEF rates & calc | Hand-derived | ±€300 per year | 2 |
| Austria | 2025 | BMF Brutto-Netto-Rechner | Hand-derived | ±€300 per year (engine output not yet pinned against BMF) | 0 |
| Netherlands | 2025 | Belastingdienst — Handboek Loonheffingen | Hand-derived | ±€500 per year | 2 |
| Belgium | 2025 | SPF Finance — Tax-Calc | Hand-derived | ±€500 per year | 1 |
| Switzerland | 2025 | ESTV Tax Calculator | Hand-derived | ±CHF 500 per year (engine output not yet pinned against ESTV) | 0 |
| China | 2025 | State Tax Administration (国家税务总局) IIT calculator | Hand-derived | ±¥3,000 per year (mostly from per-city SI+HF base ceilings, not modelled) | 2 |
United Kingdom
Reference: HMRC Estimate your Income Tax. HMRC is the UK tax authority; the ready-reckoner uses the same logic as PAYE itself, so it's the closest thing to an oracle.
Tolerance: ±£0.05 on each fixture. Fixtures: 23. Tax year: 2025/26.
Cases hand-derived from HMRC bands (Personal Allowance, basic/higher/additional + PA taper above £100,000), then locked in as fixtures. Covers NI Class 1 thresholds + UEL, student-loan plans 1/2/4/5 + postgrad, and pension as net-pay. Scotland’s separate 5-band schedule (Starter 19 % → Top 48 %) is implemented and selectable via the region dropdown on /uk; Welsh + N. Irish rates use the rUK schedule. Headless HMRC scraper is on the roadmap.
Germany
Reference: BMF Lohn- und Einkommensteuerrechner. The Bundesfinanzministerium calculator is the legally-binding reference (the Programmablaufplan). Scraped via the Handelsblatt embed because the embed exposes a friendlier DOM.
Tolerance: ±€20 / month on net (±€240/yr); Lohnsteuer ±€240; Soli + Kirchensteuer ±€50. Fixtures: 29. Tax year: 2026.
Steuerklasse I covered (single, no children). All 16 Bundesländer respected (8 % vs 9 % Kirchensteuer for BY/BW vs the rest). Steuerklassen II–VI, Midijob, PKV, and the §32a 2026 zone-2 polynomial constants are still pending. Snapshot regenerated by `pnpm verify:de` (Playwright).
United States
Reference: SmartAsset state paycheck calculators. The IRS publishes no public gross-to-net calculator; SmartAsset is the de-facto industry reference and the one professional payroll teams audit against. The portfolio's rule that engines pin to a government calculator has the United States as its explicit exception.
Tolerance: ±$5 on each fixture. Fixtures: 10. Tax year: 2025.
Federal brackets + standard deduction, FICA (SS + Medicare), Additional Medicare surtax; California / New York / Texas / Florida / Illinois. Single filer only at v1; MFJ / MFS / HoH and the remaining 45 states roll out in subsequent releases. Headless SmartAsset scraper is on the roadmap.
France
Reference: URSSAF mon-entreprise. URSSAF is the French social-security collector. mon-entreprise is its public-facing simulator — government source, brut → net → net-après-impôt in one pass. Used because the DGFiP simulator at impots.gouv.fr is auth-gated and harder to scrape politely.
Tolerance: ±€500 per year. Fixtures: 3. Tax year: 2025.
Cotisations sociales, CSG/CRDS, abattement 10 % capped at €14,426, PAS at marginal rate. Cases cross-checked against URSSAF mon-entreprise; single filer v1. Quotient familial and prélèvement à la source individualisé deferred. Headless mon-entreprise scraper is on the roadmap.
Spain
Reference: Cinco Días sueldo neto. AEAT (Spanish tax authority) does have a renta simulator, but it's auth-gated. Cinco Días (Grupo PRISA) is the Spanish-industry reference calculator used in financial-press coverage; pinned to here as the closest publicly-scrapeable proxy. AEAT direct verification is on the roadmap.
Tolerance: ±€500 per year. Fixtures: 2. Tax year: 2025.
IRPF state + autonomic brackets, Seguridad Social, mínimo personal y familiar baseline. Full 17 comunidades autónomas now selectable: 5 with published 2025 autonomic tariffs (Madrid, Catalunya, Comunitat Valenciana, Andalucía, Galicia); the remaining 10 común-régimen communities fall back to the state schedule on the autonomic half (within ±1 % per band of their published values). País Vasco + Navarra are FORAL — their separate tax systems are not modelled; engine returns a state-schedule approximation with a "foral approximation" caveat in the result.
Canada
Reference: CRA Payroll Deductions Online Calculator. CRA is the Canadian tax authority; its payroll calculator is the canonical reference used by payroll software. Engine implements federal + 10 provinces (no territories yet); Quebec gets its full special-case treatment (QPP, QPIP, reduced EI, 16.5 % federal abatement).
Tolerance: Engine output frozen against itself; CRA scraper deferred. Fixtures: 13. Tax year: 2025.
All 10 provinces (ON, QC, BC, AB, SK, MB, NS, NB, PE, NL) with their published 2025 brackets. v0 caveats: provincial surtaxes (ON 20/36 %, PE 10 %) deferred; CPP2 + QPP2 (4 % on YMPE→YAMPE) deferred; federal BPA phase-out above $177,882 deferred; Ontario Health Premium not modelled. Territories (YT, NT, NU) not yet implemented. Bracket values sourced from CRA T4127 + provincial budgets Q4 2024; full Playwright scraper against CRA Payroll Online Calculator on the roadmap.
Italy
Reference: Agenzia delle Entrate — IRPEF rates & calc. Agenzia delle Entrate publishes the official IRPEF schedule and addizionali tables; the rate values are authoritative even though the agency doesn't ship a public gross-to-net web calculator like HMRC does.
Tolerance: ±€300 per year. Fixtures: 2. Tax year: 2025.
IRPEF 2025 three-tier scale (23 / 35 / 43 %), INPS employee composite 9.49 %, detrazione lavoro dipendente as a flat €1,880 base allowance. All 20 regioni selectable with per-region addizionale regionale (1.23 %–3.33 % top marginal) and a flat 0.8 % addizionale comunale (national blended average). Per-commune comunale detail (8,000+ comuni) deferred to F2-IT. Detrazione lavoro is a flat allowance rather than the real income-tapered tax credit; income-tapered curve deferred.
Austria
Reference: BMF Brutto-Netto-Rechner. The Austrian Bundesfinanzministerium calculator is the official reference. Austria's Einkommensteuer and Sozialversicherung are uniform nationally; the BMF tool asks for Bundesland only to compute the Pendlerpauschale (commuter allowance), which is not modelled at v0, so the engine intentionally omits the Bundesland input.
Tolerance: ±€300 per year (engine output not yet pinned against BMF). Fixtures: 0. Tax year: 2025.
Lohnsteuer 2025 progressive scale, SV employee composite ~18.12 % capped at HBG €77,400. Familienbonus Plus €2,000/child and Alleinverdienerabsetzbetrag applied for married + children. 13th/14th month special 6 % rate not modelled (F2-AT). Bundesland-specific Pendlerpauschale + Verkehrsabsetzbetrag commuter uplifts deferred to F2-AT. Engine output not yet pinned against the BMF Brutto-Netto-Rechner — fixture set is on the roadmap.
Netherlands
Reference: Belastingdienst — Handboek Loonheffingen. The Belastingdienst (Dutch tax authority) doesn't ship a public consumer-facing gross-to-net web calculator — the Loonheffingen-rekenmodule is an employer-payroll tool. We pin to the published Box 1 schedule + heffingskorting tables from "Handboek Loonheffingen 2025", which are the authoritative rate source professional payroll software audits against.
Tolerance: ±€500 per year. Fixtures: 2. Tax year: 2025.
Box 1 (work + home) 2025 three-tier schedule (35.82 / 37.48 / 49.5 %) — loonbelasting + premies volksverzekeringen combined. Algemene heffingskorting (max €3,068, tapered €28,406 → €76,817) + arbeidskorting (max €5,599, piecewise-linear €11,491 → €43,071 → €128,047). National only — no regional variation, matching the Belastingdienst tool. v0 caveats: ZVW employer-paid (not deducted from gross); pension premium not modelled (CAO-dependent); fiscal-partner + IACK (working-parent credit) deferred to F2-NL.
Belgium
Reference: SPF Finance — Tax-Calc. SPF Finance / FOD Financiën is the Belgian tax authority. The official Tax-Calc simulator asks for commune of residence because additionnels communaux vary 0–9 % across the 581 communes.
Tolerance: ±€500 per year. Fixtures: 1. Tax year: 2025.
Federal IPP 4-tier scale (25 / 40 / 45 / 50 %), ONSS employee 13.07 % composite, quotité exemptée €10,570 + per-child increments, huwelijksquotient for married sole-earner. Three regions selectable (Flanders, Wallonia, Brussels-Capital); the communal additionnel is region-blended (FLA 7.0 % / WAL 8.0 % / BRU 6.5 %) from SPF Finance 2025 commune statistics. Per-commune granularity deferred (F2-BE); regional tax adjustments (Flemish/Walloon/Brussels income-tax cents) folded into the blended communal average for v0.
Switzerland
Reference: ESTV Tax Calculator. The Federal Tax Administration (Eidgenössische Steuerverwaltung) calculator is the binding reference for federal + cantonal taxes. The real ESTV tool also asks for municipality of residence (Gemeinde) to compute the municipal multiplier; v0 stops at canton.
Tolerance: ±CHF 500 per year (engine output not yet pinned against ESTV). Fixtures: 0. Tax year: 2025.
Federal direct tax + AHV/IV/EO + ALV employee shares. All 26 cantons selectable with their published 2025 cantonal multipliers. v0 caveat: municipal multiplier omitted — cantonal multiplier alone explains ~80 % of the cantonal+communal spread; municipality-level granularity deferred to F2-CH. Engine output not yet pinned against the ESTV calculator — fixture set is on the roadmap.
China
Reference: State Tax Administration (国家税务总局) IIT calculator. China's State Tax Administration calculator covers only the national IIT — it does NOT cover social insurance + housing fund (五险一金), which are governed by each city's 人社局 and vary materially. For accurate take-home pay the engine combines the national IIT with per-city SI+HF rates sourced from each city's local labour bureau.
Tolerance: ±¥3,000 per year (mostly from per-city SI+HF base ceilings, not modelled). Fixtures: 2. Tax year: 2025.
Comprehensive Income (综合所得) 7-tier IIT scale (3 %–45 %), basic deduction ¥60,000/yr, child education special additional deduction ¥24,000/yr per child. SI+HF employee composite rate varies per city: Beijing/Hangzhou ~22.5 %, Shanghai ~17.5 %, Shenzhen ~14.5 %; 6 tier-1/2 cities (Beijing, Shanghai, Shenzhen, Guangzhou, Hangzhou, Chengdu) plus a national-average fallback. Per-city contribution base CEILINGS (~3× local average wage) deferred (F2-CN); other special additional deductions (housing, elderly care, vocational study) deferred.
The US exception
Every other country on the site is pinned to its government-operated calculator. The United States is the explicit exception: the IRS publishes no public gross-to-net tool that covers state-level withholding, and the state DOR calculators differ wildly in completeness. SmartAsset is the de-facto industry reference, used by professional payroll teams as their own audit baseline, and is the most consistent multi-state source available. If the IRS or a state DOR ever ships a public calculator, the US engine will switch its reference and the change will be flagged here.
What “within tolerance” means in practice
A tolerance of ±£0.05 per fixture (UK) means: for every fixture in the test matrix, the engine’s annual net result is within five pence of the hand-derived number cross-checked against HMRC’s ready-reckoner. The wider tolerances (±€20/month for Germany, ±€500/year for France and Spain, ±$5 per case for the US) reflect known undocumented constants in the reference calculators — for example, the BMF’s 2026 §32a zone-3 polynomial coefficients aren’t publicly published. These tolerances narrow as the underlying coefficients become available or as we land live scrapers for each country.
What the engine doesn’t do
The calculator is a pre-tax-code estimator: it computes what the published rules say a typical employee on a standard tax code should net. It does not model:
- Prior-year underpayments or HMRC tax-code adjustments (UK), Steuerklasse changes mid-year (DE), zonal city-tax overlays beyond the listed states (US).
- Salary-sacrifice schemes, share-scheme withholdings, or employer-administered benefits-in-kind.
- Foreign-tax credits, double-taxation treaties, or non-resident scenarios.
- Family-status optimisations (UK marriage allowance, DE Steuerklassen II/III/IV shifts, FR quotient familial, ES mínimo familiar above the baseline).
These are deliberate omissions for the v1 surface, not bugs — the bracket pages would become unusable if every input had to handle every edge case. They are tracked on the roadmap and prioritised by traffic.
Reporting a discrepancy
If your payslip disagrees with a result here by more than the published tolerance, mail info@mytakehomepay.appwith the inputs you typed (gross + country + options) and the number from your country’s reference calculator. Bugs with a reproducer get fixed in the same release cycle.