What is tax residency?
Tax residency is the status that decides which country, and often which state or province, has the right to tax your worldwide income rather than just the income you earned inside its borders. It is not the same thing as citizenship, and it is not the same thing as immigration status. You can hold one country's passport, live on another country's visa, and be tax resident in a third.
Almost every jurisdiction decides the question the same two ways: by counting the days you were physically present, and by asking where your life is actually centred. The day count is the part people can control and the part that gets audited, which is why the 183-day rule is the single most recognised threshold in international tax.
This guide defines the terms, explains how the major tests work, and links the rule page for every jurisdiction we cover.
The definition, in one paragraph
You are a tax resident of a jurisdiction when its law says you have a close enough connection to it that it can tax you as one of its own. In practice that means being taxed on your worldwide income, from every country, rather than only on income sourced locally. A non-resident is typically taxed only on what they earn inside that jurisdiction. The gap between those two treatments is why residency is worth arguing about, and why tax authorities audit it.
Because each jurisdiction writes its own definition, the tests overlap. Two countries can both conclude that you are resident in the same year. That outcome is normal, not an error, and it is what tax treaties exist to resolve.
The 183-day rule, and why it is not one rule
The 183-day rule is the most common residency threshold in the world: spend more than half a year in a jurisdiction and it generally treats you as resident. 183 is simply the smallest whole-day majority of a 365-day year.
The trap is that 'the 183-day rule' describes a family of rules, not one rule. The counting period differs: most countries use the calendar year, the UK uses 6 April to 5 April, and Schengen uses a rolling 180-day window rather than a fixed year. The threshold itself differs: India and Malaysia use 182 days, Thailand 180, New York 184, and several US states use seven months or 200 days. What counts as a 'day' differs too: some jurisdictions count any part of a day as a whole day, others require you to be present at midnight, and some exclude transit days.
The US goes further and does not use a plain 183-day count at all. Its Substantial Presence Test weights three years together: every day this year, a third of last year's days, and a sixth of the year before that. You can be under 183 days this year and still be a US tax resident.
Residence vs domicile: they are different things
Residence is generally about where you are. Domicile is about where you belong. Domicile is the jurisdiction you treat as your permanent home, the one you intend to return to, and it is deliberately sticky: you keep your existing domicile until you clearly acquire a new one, and simply leaving is not enough.
That distinction decides real cases. Most US states will tax you as a resident on either basis: if the state is your domicile, or if you are a 'statutory resident' because you kept a permanent place of abode there and spent more than the threshold number of days in the state. Someone who moves from New York to Florida but keeps a Manhattan apartment and returns often can lose on the day count even after genuinely changing domicile.
The UK and Ireland historically ran the sharpest version of this split through their non-domiciled regimes, where residence determined that you were taxed and domicile determined how much of your foreign income was in scope.
Statutory residence tests and facts-and-circumstances tests
A statutory residence test replaces judgement with arithmetic: meet the stated conditions and you are resident, regardless of how you feel about it. The UK Statutory Residence Test is the most developed example, combining automatic overseas tests, automatic UK tests, and a 'sufficient ties' test that scales the day threshold to how many connections you have to the UK.
A facts-and-circumstances test does the opposite: it weighs where your home, family, work, bank accounts, doctors, and vehicles are. California is the best-known example, and it can reach someone who never crosses a clean day threshold at all.
Most jurisdictions use both, applying a day-count rule first and a connection-based rule as a backstop. That is why a good day count is necessary but not always sufficient.
When two countries both claim you: treaty tie-breakers
If two countries each conclude you are resident, and they have a tax treaty, the treaty's residence article decides which one wins for treaty purposes. Most treaties follow the OECD Model's Article 4 tie-breaker, which runs through a fixed sequence: first, where you have a permanent home available to you; then, if you have one in both, where your centre of vital interests lies; then your habitual abode; then your nationality; and finally, if none of those settle it, by agreement between the two tax authorities.
The order matters. You do not get to pick the factor that suits you, and you cannot skip to nationality because it is the easiest to prove. Each step is only reached if the previous one is genuinely inconclusive.
What actually decides an audit
Residency disputes are won and lost on evidence of where you physically were, recorded at the time. A calendar reconstructed after the fact from memory, credit-card statements, and photos is worth far less than a contemporaneous log kept as you travelled, and auditors say so explicitly.
The practical implication is that the day count is not a year-end exercise. If you are anywhere near a threshold in any jurisdiction, the record has to exist before the question is asked. That is the problem Tax Days is built to solve.
Rule types
- 183-day ruleThe 183-day rule is the most common tax-residency threshold worldwide. The full list of countries and US states using it, with each specific threshold.
- Substantial Presence TestThe Substantial Presence Test is a 3-year weighted day-count formula the US uses for non-citizens: this year in full, a third of last year, a sixth before.
- Rolling windowRolling-window rules count days inside a moving window, like 90 days in any 180 for Schengen. The window advances daily, so they are harder to plan around.
- Statutory Residence Test (UK)The UK SRT is a three-stage residency test: automatic non-resident tests, automatic resident tests, then a sufficient-ties test using day count plus UK ties.
- Days + Abode (statutory residence)New York, New Jersey, Massachusetts, Connecticut and Pennsylvania trigger statutory residence on 184+ days AND a permanent place of abode. Both are required.
- Facts and circumstancesFacts-and-circumstances residency tests weigh the totality of your connections, home, family and business, rather than a fixed day count. California leads.
Frequently asked questions
What is tax residency?
Tax residency is the status that gives a country the right to tax your worldwide income rather than only the income you earned there. Most countries decide it by counting the days you were physically present, usually against a 183-day threshold, and by assessing where your permanent home and personal ties are. It is separate from citizenship and from immigration status.
What does it mean to be a tax resident?
It generally means you are taxed the same way a local is: on your income from everywhere in the world, not just income arising inside that country. Non-residents are usually taxed only on locally sourced income. It can also bring filing, disclosure, and foreign-asset reporting obligations that non-residents do not have.
Is tax residency the same as citizenship?
No. Citizenship is a legal nationality; tax residency is a tax status you can acquire or lose by moving. The United States is the notable exception among major economies, taxing its citizens on worldwide income wherever they live, which is why US citizens abroad still file even when they are tax resident somewhere else.
How many days can I spend in a country before becoming a tax resident?
The most common answer is 183 in a year, but it varies: India and Malaysia use 182 days, Thailand 180, and some US states use 200 days or seven months. The counting period varies too (the UK tax year runs 6 April to 5 April), and the US Substantial Presence Test weights three years together, so you can cross it on well under 183 days in the current year.
What is the difference between residence and domicile?
Residence is generally where you are, measured by presence and ties, and it can change year to year. Domicile is where you permanently belong, it reflects intent as much as location, and it is deliberately hard to shed: you keep your existing domicile until you clearly establish a new one. Many jurisdictions tax you as a resident on either basis.
Can I be a tax resident of two countries at once?
Yes, and it is common. Each country applies its own test, so both can conclude you are resident in the same year. If a tax treaty exists between them, its tie-breaker rules decide which country treats you as resident for treaty purposes, working through permanent home, centre of vital interests, habitual abode, and nationality in that order.
Can I be tax resident nowhere?
In theory, briefly, and it is far less useful than it sounds. Domicile rules, the stickiness of your previous residence, and citizenship-based taxation mean that most people who believe they are resident nowhere are in fact still resident where they left. Banks and tax authorities also increasingly require a tax residence and a tax identification number for reporting purposes.
Track all of it in one app
Tax Days runs every rule in this guide on your iPhone, a live day count across US states, federal SPT, Schengen, and 200+ countries.
