Methodology and sources
Last reviewed:
Kalkulo calculators are built around local market rules. We prefer primary government, tax-authority, social-security, central-bank and official legal sources, then document any simplification that affects the result.
The goal is not to create a single European formula. Each calculator should answer a specific local question using the rule set, terminology and currency that a user in that market expects. When a rule has exceptions, regional branches or eligibility conditions, the page explains the assumption or exposes it as an input when that is practical.
Review process
- Each calculator has a market, currency, locale and effective data date.
- Formula inputs are checked against official sources before publication.
- Worked examples are reconciled against the calculation engine.
- Material updates are reflected in the page's update date and explanatory copy.
Source hierarchy
We prefer primary sources: tax authorities, ministries, social-security agencies, central banks, official legal databases and regulator guidance. If a primary source is hard to use, we may use official explainers or public calculators from the same authority to confirm the interpretation. Commercial articles, forums and generic summaries are not enough on their own for a formula or threshold.
| Calculator area | Preferred source type |
|---|---|
| Salary, income tax and self-employment | Tax authority tables, social-security rules, official payroll guidance and legal texts. |
| VAT and business thresholds | VAT authority pages, finance ministry guidance and official rate schedules. |
| Loans, mortgages and property | Central-bank guidance, consumer-credit rules, tax authority property pages and public formulas. |
| Benefits, leave and severance | Employment law, social-insurance agencies, labour ministries and official benefit calculators. |
Testing before publication
A calculator is checked in several ways before it is treated as production-ready. The default inputs must produce finite results, result rows must have labels and values, worked examples must match the engine, generated pages must have canonical metadata, hreflang clusters must be reciprocal, and browser smoke tests check mobile layout, consent-safe scripts and performance budgets. These checks do not replace human judgement, but they catch many regressions that would otherwise turn into thin or misleading pages.
Limits
Results are estimates for informational use. They can differ from official assessments because of rounding, local exemptions, family circumstances, deductions, timing, exchange-rate treatment or rules not captured by a simplified calculator.
The page-level FAQ and source table are part of the methodology. They should tell you what the calculator includes, what it leaves out, when the data was last checked and where to verify the underlying rule. If a calculator result matters for a tax return, employment decision, benefit claim, legal deadline or credit agreement, treat Kalkulo as a planning aid and confirm the final figure with the relevant official body or a qualified adviser.