Each public calculator starts from a country tax-rule file that defines the tax year, currency, pay-period defaults, personal allowances, social contributions, income tax brackets, and local or regional tax layers where those are modeled. The same structured rule powers the input form, charts, salary-period breakdowns, and source notes.

This keeps the site more useful than a generic percentage estimate. A person comparing a job offer can enter yearly, monthly, weekly, daily, or hourly pay, then review the net result next to tax split, effective tax rate, median salary, and minimum wage context for that country.

Estimate-only internal models are not promoted as public calculators until they have enough country-specific source coverage. Public pages focus on reviewed routes with clear assumptions, limitations, and links to source material.