Methodology

1. Primary sources only

We take figures from the body that sets them: the Canada Revenue Agency for federal tax, CPP and EI; Revenu Québec and Retraite Québec for Quebec tax, QPP and QPIP; each provincial or territorial finance ministry for its brackets and credits; CMHC for insurance premiums; OSFI and the Department of Finance for mortgage rules; and the Bank of Canada for interest rates. We do not copy from banks, blogs or other calculators. When two official pages disagree, we follow the one used for actual payroll or filing and note the conflict in the data file.

2. Payroll formulas, not approximations

The take-home pay calculator implements the CRA's T4127 Payroll Deductions Formulas, the document every Canadian payroll system follows, including its treatment of the enhanced CPP deduction, the base-CPP and EI credits, the Ontario surtax and health premium, provincial tax reductions and the Quebec abatement. Quebec provincial tax follows Revenu Québec's TP-1015.F. Mortgage math follows the semi-annual compounding required by section 6 of the Interest Act.

3. Versioned data with provenance

Every annual figure lives in a data file for its tax year, stored with the name and URL of its source and the date it was last verified. Nothing is typed into a page by hand: the key-facts blocks, worked examples and sources lists on tool pages are generated from those files, so they cannot drift out of sync with the calculations. When January figures arrive, a new year file is added and the old one stays available.

4. Tests against hand-worked official examples

The calculation engine has no user-interface code and is covered by automated tests. Each test works an example by hand from the official formula, for instance a $60,000 salary in each province, CPP at the ceiling, or a $100,000 mortgage at 5% over 25 years, and the engine must match to the cent. The site cannot be published if any test fails.

5. Re-verification

An automated check confirms that every figure has a source, every source link resolves, and no data file is older than a set age without being re-checked. A separate review re-reads each source and compares figures, and the founder spot-checks results against the CRA's payroll calculator and bank calculators. Changes are logged on the changelog.

6. What we deliberately leave out

Each tool page lists what it does not model. We would rather show a clearly scoped, correct number than a vaguer one that pretends to cover every case. Where an answer depends on assumptions, such as your tax rate in retirement, the assumption is an input you can change, not a hidden constant.

Corrections

If you find an error, contact us. Confirmed errors are fixed within days and recorded in the changelog with the date and what changed. See the editorial policy.

Written and maintained by Nishant Malik, founder of GlassLayer.