Where the numbers come from
Tax rules come from legislation and official tax-authority publications. We keep a source record, the relevant section and dated evidence for the formulas. Calculator examples use the same rules as the interactive tool.
What verification means
Automated tests check reference arithmetic, boundary values and supported inputs. Source monitoring checks whether published evidence has changed. These are implementation checks. We do not claim a qualified accountant has reviewed every result.
Each tool lists its country, tax year, starting input and exclusions. A federal bracket calculation must not be described as total tax or take-home pay.
How AI is used
AI assists with research, writing and software development. The public calculators use fixed arithmetic, not AI-generated answers. The update system can prepare a proposed change, but it cannot publish a new formula without the validation process.
We do not invent personal experience, professional credentials, customer quotations or review dates. Plain wording should make an explanation easier to understand, not conceal how it was prepared.
When sources change
An unresolved change or expired source verification pauses the affected interactive estimates. Checking an unchanged source does not mean the article received a new editorial review. Historical examples remain labelled with their year and evidence date.
Report a correction
Email [email protected] with the page, tax year, a made-up example and the official source that explains the issue. Please leave out tax identifiers, returns, bank details and passwords.
We assess the reported issue against the tool’s scope. Confirmed material corrections should explain what changed and which results were affected.