Know how the
answer was checked.

Who publishes the tools and guides?

DollarMath publishes the calculators, explanations and worked examples. Marc Pelland created the site and is the contact for feedback and corrections. Calculator and guide authorship is attributed to DollarMath.

“Checked by DollarMath” describes internal source review and calculation checks. External professional audit, certification and tax-authority or lender approval have not been obtained.

How calculation checks work

Financial formulas are kept separately from the interface and regional datasets. Automated tests cover supported inputs, invalid values, zero rates, rounding, payment frequencies and jurisdiction boundaries. Existing checks also cover saved-plan compatibility and preservation of scenario assumptions.

Worked examples use separately derived arithmetic where possible. For example, the $100 mortgage prepayment example is checked against a separate 50-digit Decimal recurrence. The Ontario and Québec salary comparison reconciles separately checked tax and contribution components. The remaining-pay example reconciles each deduction to the cent. Tests also keep published answers and structured data aligned.

Passing tests gives evidence for the covered examples. It does not prove every possible financial situation, every lender’s contract or an official payroll calculation is supported.

Sources, years and review dates

The sources page lists official references, dataset versions, effective periods and review deadlines. Government and regulator sources take precedence for policy claims. A strategy owner’s commercial explanation is labelled as such. Accessible sources can be monitored for text changes; a detected change is a review signal, not permission to publish new rules automatically.

A guide’s content-check date describes its editorial check. It does not reset a numerical dataset’s review date, make the example a current market quote or extend a 2026 model to another tax year. Dated guides keep their stated year. New years and jurisdictions require their own sources and checked examples.

Assumptions are part of the result

Examples state their currency, period, region and major exclusions. User-entered rates and defaults are assumptions, not verified offers. An annual basic-credit salary estimate, an entered-withholding remaining-pay planner and a tax-relief timing illustration are different models.

Opening an older saved plan recalculates supported inputs with the current engine. Exports identify the rule version. Spreadsheet exports are value snapshots; JSON backups restore editable plans. Keep a copy when a historical result matters.

Report a result that needs attention

Use the creator contact with the page, country/province, year, made-up inputs, observed result and expected result or official reference. Leave out account details, SINs, tax documents and other sensitive records. Reporting is optional and separate from using the tools.

A calculation change needs a reproducible example, a source or derivation, and regression checks before release. Versioned implementation and release notes track changes. This page is not a complete historical correction register; an example’s date alone does not establish a review by someone outside DollarMath.

Information, not financial advice

DollarMath provides calculators and information for educational purposes. The tools do not determine suitability, deduction eligibility, lender approval or your final tax liability. Read the full disclaimer and the scope beside the calculator you are using.