What is Worldwide Taxation?

How it works

Worldwide taxation is the default in nearly every developed economy. Once you cross the residency threshold, the country claims jurisdiction over all your income — domestic salary, foreign rental income, dividends from a Hong Kong holding, capital gains realised on a Brazilian property, fees received in crypto from a Singapore client. Where it was earned doesn't matter; where you were resident when it was earned does.

The mechanism is taxation by residency. Cross the threshold (usually 183 days, sometimes a center of vital interests test) and the country starts assessing you on global income. Lose residency cleanly and the obligation ends going forward — though many worldwide-tax countries impose an exit tax on unrealised gains at the moment of departure: US §877A for covered expatriates, France art. 167 bis CGI, Germany Wegzugsbesteuerung.

The United States adds a layer that no other major economy matches: it taxes its citizens and green card holders regardless of where they live. A US citizen running a SaaS company from Lisbon owes US tax on the worldwide profits of that company every year, plus FBAR and FATCA reporting on his foreign accounts. The only escape is renunciation — and even then, exit tax applies if the net-worth or income tests are tripped.

Relief mechanisms exist precisely because worldwide taxation produces double taxation by construction. Two main tools soften the impact: foreign tax credits, which let you offset taxes paid abroad against your home-country liability; and double-tax treaties, which allocate which country gets primary taxing rights and which one yields. For US citizens specifically, the Foreign Earned Income Exclusion shelters around $126,500 of earned income (2024 figure, indexed) — useful for salaried expatriates, useless for capital gains or US-source business income.

Examples

• A French resident sells US shares. A French tax resident with a brokerage account books a €120k capital gain on Apple stock. France taxes it at the 30% PFU flat rate. Under the France-US treaty, the US has no taxing right over capital gains realised by a French resident on movable property — France collects 30%, period, no FTC needed.
• A US citizen consults from Dubai. Earns $400k in 2026, banks in the UAE, no US presence. The UAE has no personal income tax. The IRS still assesses worldwide tax on the $400k — minus FEIE on the first $126,500 — leaving roughly $273,500 taxable at federal rates plus self-employment tax. The Dubai move saves nothing on US federal income tax; only renunciation does.

Common mistakes

• Confusing residency with presence. Spending zero days in your old country does not, by itself, break worldwide tax obligations there. France, Germany, Spain and the UK can all keep you resident on permanent home, family, or vital interests grounds — see tax residency.
• Underestimating exit tax. Founders plan the residency move and skip exit-tax modelling. France triggers exit tax above €800k of latent gains; Germany applies extended limited tax liability for 10 years on German-source income; Spain has a 4-year shadow rule for moves to low-tax jurisdictions.
• Assuming a territorial system means zero tax. Paraguay, Hong Kong, Singapore, Panama, Georgia (under the HNWI / IT regimes) tax foreign-source income at zero or low rates — but only foreign-source. Local salary, local rental income, and locally-sourced consulting fees stay taxable.
• Ignoring CFC and Subpart F. Owning a Cayman or Estonian company doesn't shelter you from worldwide taxation if your home country has CFC rules. The income flows through to you whether or not it is distributed — designed precisely to neutralise this kind of structure.