News22Times builds every calculator from official government sources (IRS, HMRC, ATO, CRA and state or provincial agencies), tests it against the authority's own worked examples and estimators, and shows the tax year and last review date on each page. Results are estimates, not advice.
This page explains how News22Times builds, tests and updates its calculators, and the limits of the results they produce.
Principles
- Primary sources first. Rates, thresholds and formulas come directly from the body that sets them, not from other calculator websites.
- One country, one rule set. Pay and tax calculators are built separately for each country and, where it matters, for each state, province or territory.
- Show the working. Results include a breakdown so you can see how the total was reached, and each calculator lists its sources.
- Date everything. Every calculator shows the tax year it covers and the date it was last reviewed.
Official sources we use
| Country | Main sources |
|---|---|
| United States | IRS (including Publication 15-T for federal withholding), Social Security Administration wage base, and each state’s department of revenue |
| United Kingdom | HMRC rates and thresholds for employers, GOV.UK guidance on Income Tax, National Insurance, student loans and Stamp Duty Land Tax |
| Australia | Australian Taxation Office (ATO) tax rates and tables, Medicare levy and study loan thresholds, and each state or territory revenue office for transfer duty |
| Canada | Canada Revenue Agency (CRA) payroll deductions formulas, provincial tax rates, CPP/QPP and EI rates, and provincial land transfer tax rules |
How we test
- We build the formula from the official publication.
- We test it against worked examples published by the authority.
- We cross-check sample results against the authority’s own estimator where one exists, such as the IRS Tax Withholding Estimator, HMRC’s Income Tax estimator, the ATO simple tax calculator and the CRA Payroll Deductions Online Calculator (PDOC).
- We test edge cases: thresholds, very low and very high incomes, and zero values.
- A second review checks the page before it goes live.
Updates
Tax and pay rules change with budgets and new tax years. We review affected calculators when new rates are announced and at least once a year. When rules change part-way through a year, the calculator states which rules it applies.
Assumptions and limits
- Results are estimates for general information. They are not financial, tax or legal advice.
- Calculators use standard assumptions, which are listed on each page, such as a standard tax code or no other income.
- Your real figures may differ because of personal circumstances, employer payroll timing, rounding or deductions the calculator does not include.
- Amounts are rounded for display; internal calculations keep full precision until the final step.
Privacy of your inputs
Calculators run in your browser. The numbers you type are not sent to or stored on our servers.
Found a mistake?
Please tell us with the calculator name, your inputs and the result you expected. Confirmed errors are fixed, and the review date on the page is updated.
Key facts
- Every calculator lists the official sources its formula is based on.
- Pay and tax tools are built separately for the US, UK, Australia and Canada.
- Each calculator shows the tax year it covers and the date it was last reviewed.
- Calculations run in your browser; inputs are not stored.
Frequently asked questions
Where do your tax rates come from?
Directly from the official publications of the IRS, HMRC, the ATO, the CRA and state or provincial revenue agencies.
How do you check the calculators are right?
We test against the authority's own worked examples and compare sample results with official estimators such as HMRC's Income Tax estimator and the CRA's Payroll Deductions Online Calculator.
Why might my result differ from my payslip?
Personal circumstances, your tax code or W-4, benefits, employer payroll timing and rounding can all change the real figure.