DoubleTaxation

Determines the person's tax residence between the version's home state and another country, step by step. Without all answers it returns status "needs_answer" and the next question (id, text, options); ask the user and call again with all answers collected so far. When complete it returns status "done": the conclusion with reliability %, how each law treats the person, the treaty tie-breaker, where and which taxes apply, next steps (certificate of residence, resident / non-resident obligations, steps when leaving), exit tax and the year of the move (with "move"), what the result does not cover, the legal basis (norms with links) and court practice, optional per-income-type rules, the disclaimer and a link to the same result on doubletaxation.app. Texts are in the language of the version.

Business tax calculator for a resident of one country and one sector (activity): every legal form (sole proprietor, own company) under every available tax system — total tax and contributions, what remains, rate, line items, why a system is unavailable for the sector or amount, conditions, legal norms; requirements for each legal form and the sector's tax features; assumptions and sources. Same calculation and ranking as doubletaxation.app (section "Business taxes"); an estimate, not tax advice.

Counts days of stay per country from the trips the user provides (country, from, to) under each country's own counting rule (calendar year, tax year, any 12 months, US substantial presence test, continuous stay): days in the counting period, the day threshold for tax residence and its legal source, the date it was reached or how many more days are needed, and Schengen 90/180 days used. The day of arrival and departure counts in both countries. It does not track anyone: it only counts the trips passed in, and they are not stored.

Whether a country levies an exit (departure) tax on individuals who give up tax residence: who pays and on what (assets, thresholds, prior residence period), deferral or relief (e.g. moving within the EU/EEA), the legal norm with a link and the date checked.

Answers general questions about tax residence and the theory behind it from the monograph by DoubleTaxation's legal expert, Yevhen Marynchak, "The Financial-Legal Link Between an Individual and the State" (2nd edition, 2020): 893 questions and answers covering what resident status is and why it exists; its history (from the citizenship principle to the residence principle, the League of Nations work of the 1920s, the OECD Model Tax Convention); economic theories of taxation (Smith, von Schanz, Wicksell–Lindahl); concepts of the "income taxpayer"; tax sovereignty and tax jurisdiction and their kinds (interstate, state, local, offshore zones); the legal status and tax legal personality of an individual taxpayer; criteria of residence and the treaty tie-breaker; source taxation; e-government; problems of the Ukrainian rules; the author's own terms and definitions. Each entry is a plain-English paraphrase with the book's section, page and a link to find the original text. Use "query" for a question (translate it into English key words); call without arguments for an overview and the table of contents. Not for a person's own status: use check_residency.

Lists the countries that can be checked against the home state of a version: whether a tax treaty is in force (title, dates, link), whether per-income treaty rules and tax burden data exist, plus the allowed citizenship options and years for check_residency.

Lists the 24 versions of DoubleTaxation. Each version is written for taxpayers of one home state (in its language) and compares it with 27 other countries. Call this first if you are not sure which version fits the user.

What to do once the tax residence is known (the same blocks as under the result on doubletaxation.app and in check_residency "done"): how to get a certificate of residence, obligations of a resident (returns, deadlines), obligations and options of a non-resident with income from the other state (treaty relief forms, refunds), U.S. citizen obligations, steps when leaving the state, the exit tax, how each state treats the year of the move, and what the conclusion does not cover. Each step has the authority, form, link and legal norm. Texts are in the language of the version.

Special and preferential tax regimes for individuals (newcomers / impatriates, employees, self-employed, investors, pensioners) in 21 countries. Filter by country, kind, status and free text. Returns per regime: official name, who it is for, the benefit, duration, how to apply, limits and risks, status (open, closed to new entrants, only for existing participants, starts later), the legal norm with a link and the date checked.

Income tax and social contributions on an annual salary in one or more countries (OECD Taxing Wages method: single person, no children, full-year employee). Returns net pay, personal rate, tax wedge and marginal rate, sorted from lowest to highest personal rate. 21 countries are fully checked; some 130 more have preliminary data (marked level "preliminary"). For up to 3 countries also the line-by-line breakdown, special tax regimes for individuals (e.g. for newcomers), assumptions and official sources.