Tax sources
Every rate, threshold and formula in our calculators comes from a government publication. This page lists them by rule set.
United States — federal
Tax year 2026 · rule version us-federal-2026.2 · effective 2026-01-01 to 2026-12-31 · Verified · last checked 2026-10-12
Rate tables 1-4 and standard deduction (section 4.14) transcribed from the text of Rev. Proc. 2025-32. Social Security wage base cross-checked between SSA and IRS Topic 751. Additional Medicare Tax thresholds by filing status read from IRS Topic 560 on 2026-10-12. Bracket base amounts in the IRS tables are reproduced by the engine in tests.
- Rev. Proc. 2025-32 — inflation-adjusted items for taxable years beginning in 2026 — Internal Revenue Service, published 2025-10-09; checked 2026-10-11
- Topic no. 751, Social Security and Medicare withholding rates — Internal Revenue Service, published 2026-09-24; checked 2026-10-11
- Topic no. 560, Additional Medicare tax — Internal Revenue Service, published 2026-10-09; checked 2026-10-12
- Contribution and Benefit Base — Social Security Administration; checked 2026-10-11
United States — states
Tax year 2026 · rule version us-states-2026.2 · effective 2026-01-01 to 2026-12-31 · Partly unverified
Per-state status is recorded on each entry. 9 jurisdictions without a wage income tax and 5 with a calculated income tax are verified against state sources. 26 states use unverified legacy parameters. 11 jurisdictions are not calculated.
- Personal Income Tax — Alaska Department of Revenue, Tax Division; checked 2026-10-12
- Employment Security Tax — taxable wage base and tax rates — Alaska Department of Labor and Workforce Development; checked 2026-10-12
- Report Tax Violations (states that Florida has no personal income tax) — Florida Department of Revenue; checked 2026-10-11
- Income tax rates — Illinois Department of Revenue; checked 2026-10-12
- Informational Bulletin FY 2026-15, What's New for Illinois Income Taxes — Illinois Department of Revenue; checked 2026-10-12
- What is the Illinois personal exemption allowance? — Illinois Department of Revenue; checked 2026-10-12
- 2026 Kentucky Withholding Tax Formula (42A003 TCF) — Kentucky Department of Revenue; checked 2026-10-12
- Form K-4, Kentucky's Withholding Certificate 2026 — Kentucky Department of Revenue; checked 2026-10-12
- Kentucky DOR Announces 2026 Standard Deduction — Kentucky Department of Revenue; checked 2026-10-12
- Withholding Tax Information by Calendar Year — Michigan Department of Treasury; checked 2026-10-12
- Tax Rates, Exemptions, & Deductions — Mississippi Department of Revenue; checked 2026-10-12
- Income Tax in Nevada — Nevada Department of Taxation; checked 2026-10-11
- Interest & Dividends Tax — New Hampshire Department of Revenue Administration; checked 2026-10-11
- Tax Rate Schedules — North Carolina Department of Revenue; checked 2026-10-12
- NC-30, 2026 Income Tax Withholding Tables and Instructions for Employers — North Carolina Department of Revenue; checked 2026-10-12
- Form NC-4, Employee's Withholding Allowance Certificate — North Carolina Department of Revenue; checked 2026-10-12
- Taxes — Individuals — South Dakota Department of Revenue; checked 2026-10-11
- GEN-34 — Income Tax Withholding — Tennessee Department of Revenue; checked 2026-10-11
- Texas is open for small business (state income tax: none) — Texas Comptroller of Public Accounts; checked 2026-10-11
- Income tax — Washington State Department of Revenue; checked 2026-10-12
- Paid Family & Medical Leave premium rate increases to 1.13% in 2026 — Washington State Employment Security Department; checked 2026-10-12
- Paid Family & Medical Leave paycheck insert, 2026 contributions — Washington Paid Family & Medical Leave; checked 2026-10-12
- WA Cares Fund — employers — WA Cares Fund; checked 2026-10-12
- About Wyoming — State of Wyoming; checked 2026-10-11
Canada — federal, provinces and territories
Tax year 2026 · rule version ca-2026.1 · effective 2026-01-01 to 2026-12-31 · Verified · last checked 2026-10-11
Federal and provincial thresholds, rates, basic amounts and CPP/QPP/EI/QPIP limits transcribed from T4127 Chapter 8 (January and July 2026 editions). Tests check that the bracket tables reproduce the K/KP constants printed in Table 8.1. Quebec provincial tax remains unverified (see the Quebec entry).
- T4127 Payroll Deductions Formulas — 122nd Edition, effective January 1, 2026 — Canada Revenue Agency, published 2026-01-01; checked 2026-10-11
- T4127 Payroll Deductions Formulas — 123rd Edition, effective July 1, 2026 — Canada Revenue Agency, published 2026-07-01; checked 2026-10-11
- Employers: Principal Changes for 2026 — Revenu Québec; checked 2026-10-11
Germany
Tax year 2026 · rule version de-2026.1 · effective 2026-01-01 to 2026-12-31 · Verified · last checked 2026-10-11
Wage tax and solidarity surcharge: see lohnsteuer-2026.ts. Contribution ceilings and employee rates for pension, unemployment and long-term care insurance are the constants of the BMF PAP 2026. The 14.6% general health rate and the 2.9% average additional rate are from the Federal Ministry of Health.
- Programmablaufplan für die maschinelle Berechnung der Lohnsteuer 2026 (Anlage 1) and pseudocode Lohnsteuer2026.xml — Bundesministerium der Finanzen, published 2025-11-12; checked 2026-10-11
- Lohn- und Einkommensteuerrechner 2026 (reference values for testing) — Bundesministerium der Finanzen; checked 2026-10-11
- Beiträge der gesetzlichen Krankenversicherung (general rate 14.6%; average additional rate 2026: 2.9%) — Bundesministerium für Gesundheit; checked 2026-10-11
- Kirchensteuer auf Abgeltungsteuer (church tax rate: 8% in Baden-Württemberg and Bavaria, 9% elsewhere) — Bundeszentralamt für Steuern; checked 2026-10-11
Poland — employment contract
Tax year 2026 · rule version pl-2026.1 · effective 2026-01-01 to 2026-12-31 · Verified · last checked 2026-10-11
Tax scale from podatki.gov.pl; contribution rates and the 30x cap from ZUS; revenue costs from biznes.gov.pl. Reference payslips were calculated by hand and are asserted in tests.
- Opodatkowanie według skali podatkowej (12% / 32%, threshold 120,000 zł, tax-reducing amount 3,600 zł) — Ministerstwo Finansów — podatki.gov.pl; checked 2026-10-11
- Jak rozliczać PIT pracownika (employee revenue costs 250 zł / 300 zł per month) — biznes.gov.pl — Ministerstwo Rozwoju i Technologii; checked 2026-10-11
- Informacja o wysokości składek na ubezpieczenia społeczne w 2026 r. — Zakład Ubezpieczeń Społecznych, published 2026-02-02; checked 2026-10-11
- 30-krotność — annual cap on the pension and disability contribution base (282,600 zł in 2026) — Zakład Ubezpieczeń Społecznych; checked 2026-10-11