183-Day Tax Residency Rule: How the Count Works

Spend 183 days in a country and you can become its tax resident. But whether day 183 itself crosses the line, which 12 months are counted and what counts as a day all differ by country, and the US uses a formula instead.

Last verified: September 2026

In short: many countries make you a tax resident once your days there pass about half a year, usually 183 days. Three details change the answer: whether the line is 183 or more (UK, Canada) or more than 183 (Spain, Portugal), whether days are counted in the calendar year, the national tax year or any rolling 12 months, and whether a part day or only a midnight counts. The US uses a weighted three-year formula. And fewer than 183 days is not automatically safe: a home, family or economic ties can make you resident anyway.

What it is: A presence test in each country's own tax law, not one international rule
Typical line: 183 days, about half a year; Thailand uses 180 and Malaysia 182
Wording: "183 days or more" and "more than 183 days" differ by one day
Counting window: Calendar year, the national tax year, or any rolling 12 months
United States: Substantial presence test: current year plus 1/3 and 1/6 of the two years before
Same number, different rule: Tax treaties use 183 days to decide who taxes a salary, not where you are resident

183 or more, or more than 183

The statutes are worded differently, and the difference is exactly one day. Under the UK's first automatic residence test you are resident if you spend 183 days or more in the UK in the tax year. Canada deems you resident if you stay 183 days or more in the year. Spain, by contrast, requires more than 183 days in the calendar year, and Portugal more than 183 days in any 12-month period, so day 183 is still under the line and day 184 crosses it.

Some countries do not use 183 at all. Thailand's line is 180 days in a calendar year, Malaysia's is 182, and Australia's test is being in the country for more than half the income year, which is 183 days in a normal year.

Exactly 183 days. You spend 183 days in Spain between 1 January and 31 December. That is not more than 183, so Spain's day test is not met. The same 183 days in the UK between 6 April and 5 April meets the UK's automatic test, because 183 or more is enough there.

Which 12 months: calendar year, tax year or rolling

The second difference is the period the days are added up in. There are three common designs:

Calendar year. 1 January to 31 December, reset every New Year. Spain, Canada, Thailand, Malta and Cyprus count this way.
A national tax year. The UK counts from 6 April to 5 April, Australia from 1 July to 30 June.
Any 12 months. Portugal counts more than 183 days in any 12-month period beginning or ending in the year concerned. Georgia uses 183 or more days in any continuous 12 months ending in the tax year, and the UAE 183 or more days in any 12 consecutive months. Greece, Estonia, New Zealand and Colombia also use a rolling window.

A rolling window catches stays that straddle New Year, which a calendar-year test never adds together.

One winter, two answers. You spend 23 September to 31 December 2025 in one country (100 days) and 1 January to 10 April 2026 there too (another 100 days). Under a calendar-year test such as Spain's, each year holds 100 days, well under the line. Under Portugal's rolling test, the 12 months from 23 September 2025 hold 200 days, more than 183, so the day test is met.

The 183-day calculator counts all three: choose the country and the window, then tap your stays.

What counts as a day

Countries also disagree on which days count. Canada counts each day or part of a day you stay in Canada. Australia counts every day you are physically present, including the days you arrive and leave. The UK counts a day only if you are in the UK at the end of it, at midnight, with an exception for some transit days. Cyprus treats the arrival day as a day in and the departure day as a day out, and Portugal counts days that include an overnight stay.

A weekend trip. You arrive on a Friday morning and fly out on Sunday evening. Where any part of a day counts, as in Canada, that is three days. Under the UK's midnight rule it is two: Friday and Saturday night.

For a side-by-side comparison of arrival, departure and transit days across tax and visa rules, see what counts as a day.

The US uses a formula, not a flat 183 days

The US substantial presence test is met if you were physically present for at least 31 days in the current year and 183 days over three years, counting all days in the current year, one third of the days in the year before and one sixth of the days in the year before that. Days commuting from Canada or Mexico, transit of under 24 hours, days you could not leave because of a medical condition and days as an exempt individual (certain students, teachers and diplomats) are left out.

120 days every year. This is the IRS's own example: 120 days in each of three years gives 120 + 40 + 20 = 180, so the test is not met.

A longer first year. Change the earliest year to 150 days: 150 in 2024, 120 in 2025 and 120 in 2026. For 2026 that gives 120 + 40 + 25 = 185, so the test is met, although no single year came near 183.

Even when the test is met, the closer connection exception can keep you a nonresident. The details, including Form 8840, are in the US substantial presence test guide.

The treaty 183-day rule is a different rule

Tax treaties use the same number for another question: which country may tax your salary. Under Article 15 of the OECD Model Tax Convention, pay for work done in a country where you are not resident is taxed only in your country of residence if three conditions are all met: you are present in the work country for no more than 183 days in any 12-month period starting or ending in the fiscal year concerned, your employer is not resident there, and the pay is not borne by a permanent establishment your employer has there. The treaty rule does not make you resident anywhere, and a treaty's own text decides the details: some older treaties count the 183 days per calendar or fiscal year instead.

Under 183 days is not automatically safe

The day count is usually one route to residence, not the only one. Examples of other routes:

Spain also treats you as resident if your main centre of economic activities or interests is in Spain, and presumes residence when your spouse and dependent minor children live there. Short trips abroad can count as days in Spain unless you prove tax residence elsewhere.
Portugal can make you resident if you keep a home there in conditions suggesting you intend to live in it as your habitual residence.
Canada can treat you as a factual resident on any number of days if you keep significant residential ties such as a home, spouse or dependants.
Australia has four residence tests, and the 183-day test is only one of them. It does not apply if your usual place of abode is outside Australia and you do not intend to take up residence there.
The UK has further automatic tests and a sufficient ties test that can make you resident on far fewer days.

When two countries both treat you as resident, the tie-breaker in their tax treaty usually decides: first a permanent home, then the centre of vital interests, then habitual abode, then nationality, and finally agreement between the two tax authorities.

Where the 183-day rule applies

The tax residency by country table lists every country covered here with its threshold and counting window. Some of the most searched:

Spain: more than 183 days in a calendar year
Portugal: more than 183 days in any 12 months
Italy: the greater part of the calendar year
Greece: more than 183 days in any 12 months
United Kingdom: 183 days or more in the tax year, plus other tests
Canada: 183 days or more in the calendar year
Australia: more than half the July–June income year
United Arab Emirates: 183 days or more in any 12 months
Georgia: 183 days or more in any 12 months
Thailand: 180 days or more in the calendar year
Malaysia: 182 days or more in the calendar year
United States: the weighted three-year formula

Beyond the day count

Tax residence and immigration status are separate. A residence permit does not make you a tax resident on its own, and a visa-free stay or a digital nomad visa does not stop the day test from running. Residence decides which country may tax your worldwide income; the income itself, treaty relief and any special regime are questions for the country's tax authority or an adviser. What you can control is the record: exact arrival and departure dates for every country, kept as you go.

AtlasDays counts your 183 days automatically

Log your trips once. Tax residence presets for more than 30 countries each count the right window, whether calendar year, a tax year starting 6 April or 1 July, or any rolling 12 months, and the US Substantial Presence Test preset applies the three-year formula. For anywhere else, the Custom Tax Residence Tracker lets you set the country, window and limit yourself. Everything stays private on your iPhone.

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FAQ

Is the 183-day rule the same in every country?

No. Each country sets its own test. Some require 183 days or more and others more than 183, the days can be counted in the calendar year, a tax year or any 12 months, and some countries use 180 or 182 days or, like the US, a formula.

Can I be a tax resident with fewer than 183 days?

Yes. Many countries have other routes, such as a permanent home, family living there or the centre of your economic interests. Spain, Portugal, Canada, Australia and the UK all have them.

Is the treaty 183-day rule the same as tax residency?

No. The treaty rule decides whether a country can tax a salary earned there by a non-resident. It applies only when you are present for 183 days or fewer in the treaty's period, your employer is not resident there and the pay is not borne by a permanent establishment in that country.

About this article: AtlasDays provides general information, not legal, tax, or immigration advice. Rules change and outcomes depend on your circumstances, so never rely on it alone: check the linked official source or ask a qualified professional.