Methodology

1. Primary Data Sources

• ①
  OECD Tax Database — Income tax rates and thresholds, social security contribution rates, and comparative tax statistics for all OECD member countries. We cross-validate our bracket data against the OECD's annual publication.oecd.org →
• ②
  National Tax Authorities — We consult official sources for each country, including: IRS (US), HMRC (UK), AT (Austria), BMF (Germany), DGFiP (France), AT Finances (Portugal), IRAS (Singapore), MoF (UAE), AADE (Greece), and others. Each country's source URL is cited on its country page.
• ③
  LLM + Brave Search Cross-Validation — Our automated pipeline (scripts/tax/refresh.py) uses large language models with live search access to flag discrepancies between our data and the latest public sources. Any discrepancy above a confidence threshold is flagged for manual review.
• ④
  Community Reports — Users can flag suspected errors via the in-app report button on results pages. Every report is reviewed by our team.

2. Calculation Model

All calculations assume a single filer with no dependents and no treaty benefits unless a specific regime is selected. The model applies:

1. Standard deduction or personal allowance (as applicable per country)
2. Progressive federal income tax brackets
3. Mandatory employee social contributions (pension, health, unemployment)
4. Any surcharges (e.g. Germany solidarity surcharge, Portugal solidarity surcharge)
5. Special regime modifications if selected (NHR/IFICI, HNWI flat tax, etc.)
6. US state tax (if a US state is selected)

We do not model: double-tax treaties, personal deductions beyond the standard deduction, employer social contributions (employer cost is noted but not included in take-home calculation), or regional/municipal taxes (except where they are the dominant factor, e.g. Swiss cantonal taxes).

3. Accuracy Target

We target 90%+ accuracy for a standard single-filer scenario compared to the official calculator or published rates for each country. This is a process target, not a legal guarantee.

Known limitations: tax brackets change mid-year in some countries; exchange rates fluctuate; special regime eligibility depends on individual circumstances not captured by the model. For accurate tax planning, always consult a qualified professional.

4. Update Cadence

Data is updated annually (typically Q1 of the tax year) and additionally when major legislative changes occur mid-year. Each country profile carries a "Last reviewed" date. Country pages showing a date older than 12 months should be treated with additional caution.

5. Disclaimer

6. How to Cite

Our data is available under CC-BY-4.0 for research, journalism, and academic use. Please cite as:

For API access or bulk dataset download, see our dataset page.