Methodology

Sources

Figures come from primary sources only: the IRS, the Social Security Administration and state revenue departments in the US; the Canada Revenue Agency, Revenu Québec and provincial finance ministries in Canada. Each tool page lists its sources and the date they were checked. If a figure can't be traced to a primary source, we leave it out rather than estimate it.

How take-home pay is estimated

We calculate the year's income tax from the brackets, deductions and credits for the tax year, add payroll contributions (Social Security and Medicare; CPP or QPP, EI and QPIP), and spread the result evenly across pay periods. This is the method most paycheck calculators use. Your employer's withholding follows IRS Publication 15-T or CRA's T4127 formulas and can differ by a few dollars a paycheck.

Rounding

Amounts are held in whole cents. Rate math is exact, and each contribution and each level of tax is rounded to the cent once.

Testing

Every jurisdiction has test cases at several incomes, worked by hand or checked against an official calculator, and the site won't build if a result drifts. Rates are reviewed each year when governments publish new figures, and the "rates verified" date on each tool shows when its figures were last checked.

What isn't included yet

US local income taxes (for example New York City, Pennsylvania and Ohio municipalities), US tax credits such as the Child Tax Credit and EITC, and Quebec's prescription drug insurance premium. Pages where these matter say so.