How the tax data is built and checked

One profile per country

Each country has one tax profile. It holds the rules for a resident individual: income brackets, allowances, social contributions, capital gains and holding periods, dividends, interest, rent, crypto, wealth tax, exit tax, special regimes and regional taxes. The engine reads only the profile. No rate is typed into a page: the tax rates by country and the wealth tax comparison are generated from the same profiles that compute your numbers in the app.

Sources

Source records identify the material we cite and record its URL and retrieval date where available. Not every source has a retained quotation. The table counts available quotations separately from source records. Withdrawn quotations are not counted as available quotations; their source identity and withdrawal history are retained. A citation or quotation is not approval of a legal claim. A source is official (primary) when it is the statute, the official gazette or the tax authority. It is secondary when it is a professional summary, for example the PwC or EY tax guides. Each rule in a profile links to the sources it rests on.

65% of the linked fields cite an official text today. The other fields rest on secondary summaries. 164 of 165 countries have at least one official source. Each country page lists its sources and says how many are official. A statute or tax authority text is preferred. A summary by PwC, Deloitte, KPMG or EY is an accepted source, and a figure that rests only on one is marked on its country page.

Tiers and the † mark

Each country page carries a tier. It says how well the figures on that page are sourced.

• Tier 1. Every figure rests on a statute, an official gazette or a tax authority page.
• Tier 2. Every figure has an accepted source. Some rest only on a PwC, Deloitte, KPMG or EY summary. Those figures carry the † mark on the country page, with the name of the publisher.
• No tier. At least one figure has no accepted source yet. The page says which.

Dated rules

Tax law changes on known dates. A profile records each announced change with the date it takes effect and its source: 541 changes in 115 countries today. A projection taxes each future year under the rules in force in that year. A proposal without a fixed date is recorded but never applied.

Testing

A test facility runs on every change to the engine or a profile. It has three parts:

• Fixed rules. 26 test investors, from 500,000 to 250 million in wealth, run through every country over 1, 3, 5 and 10 years. The run fails if a rule breaks: for example, tax that falls when income rises, an exemption that is not applied, an allowance counted twice, or a short projection that differs from the start of a long one.
• Pinned cases. 780 calculations checked by hand against the law. Each confirmed error becomes a new pinned case, so it cannot come back.
• Independent audits. AI auditors recompute sample cases from the profile data alone. A second agent then tries to prove each finding wrong. Only findings that survive go into the fixes and the pinned cases.

What we do not model

The engine covers the general rules for a resident individual. It does not cover every deduction, tax treaty, local tax or personal situation. Where a profile is less exact than the law, the profile says so in writing: 536 such notes today. Results are decision support, not a tax return.

How we keep it current

Each profile records the date of its last check against its sources. Each country page shows that date. The checks by hand run from 29 April 2026 to 23 October 2026. An automated check against PwC, Deloitte, KPMG and EY sources runs daily; it has checked 97 of 165 profiles, the latest on 11 November 2026. When it finds a difference, it corrects the profile, cites the source and adds a pinned case. When you find an error, write to us with the country and the source. We correct the profile and add a pinned case.

Every change to a published figure is listed, day by day and with its source, on What changed (also as an Atom feed).

Residence and citizenship pages

The residence and citizenship pages come from a separate set of country profiles: residence routes and citizenship rules, each fact tied to the immigration authority, the statute or the official programme page, or to one reputable summary (Henley & Partners, a Big-4 firm, an established law firm). Two automated reviews re-check them against those sources and stamp the date. Where a review has not reached a country yet, the page shows a provisional fact from a published source, marked with its publisher and the date it was read; the checked fact replaces it as soon as the review writes one. Provisional facts are never listed on What changed.

Related

Tax rates by country · Residence and citizenship by country · Wealth taxes compared · What changed · The 183-day rule by country · About Sovereign