Methodology and editorial standards

What each calculator models

Unless a page states otherwise, every calculator models a single tax resident employed by one employer for a full tax year, paid a fixed salary, claiming the standard deduction or default personal allowance, with no dependants-based credits, no self-employment income and no foreign income. This is the most common case and the only one that can be modelled honestly from a single salary input.

Which deductions are included

We include statutory income tax and the mandatory social contributions that employees actually see on a payslip, because omitting them overstates take-home pay by several percent:

• United States: federal income tax, Social Security, Medicare, and state tax where a state page exists
• United Kingdom: income tax and Class 1 employee National Insurance
• India: income tax under the selected regime, plus health and education cess
• Canada: federal and provincial income tax, CPP contributions and EI premiums
• Australia: resident income tax and the Medicare levy

Which deductions are excluded

We exclude anything that depends on facts a single salary field cannot capture: employer pension schemes, salary sacrifice arrangements, student and study loan repayments, benefits in kind, local or municipal taxes outside the pages that model them, dependants credits and surcharges tied to private insurance status. Where an exclusion commonly changes the answer by a large amount, the page says so in writing.

Where the rates come from

Rates, bands, thresholds, ceilings and levy percentages are taken only from primary government publications: the Internal Revenue Service and individual state revenue departments, HM Revenue & Customs, the Income Tax Department of India and Union Budget documents, the Canada Revenue Agency together with provincial finance ministries, and the Australian Taxation Office. We do not source figures from news summaries, aggregator sites or other calculators.

How the maths is applied

All progressive taxes are calculated slice by slice: each band's rate is applied only to the income inside that band, then the slices are summed. Capped contributions stop at their annual ceiling. Tapered allowances are withdrawn at the published rate against the correct income measure. Results are rounded for display only — never mid-calculation — so the line items always add back to the totals shown.

Review and update cycle

Each jurisdiction is re-checked when a budget, finance act or annual indexation announcement changes the numbers, and reviewed at the start of every tax year regardless. When a rate changes mid-year, the page states which tax year it models. Guides are revised alongside the calculators they describe, so an article never explains rules the tool no longer uses.

Who writes the content

Guides are written and reviewed in-house by the Global Income Tax Calculator editorial team, working directly from the statutory sources listed above rather than from secondary commentary. Nothing on this site is generated and published without a human check against the underlying legislation or authority guidance.

Corrections policy

We publish estimates, and estimates can be wrong. Reported errors are checked against the primary source, corrected within the calculator and the affected guides, and the review date is updated. Send anything that looks wrong through the contact page — we would rather fix a figure than defend it.

Privacy of your inputs

Calculations run entirely in your browser. Salary figures are never transmitted to or stored on a server, which is also why we cannot retrieve a past calculation for you.