The 183-day rule is the most quoted idea in international tax. The popular version says that if you spend more than half the year in a country you become tax resident there, and if you stay under 183 days everywhere you owe income tax nowhere. The first half is often roughly true. The second half is a myth.
In practice, the number 183 turns up in two different places. It appears in domestic residence rules, where it is usually one test among several. It also appears in tax treaties, where it decides which country may tax a salary earned during a short work trip abroad. Neither version says that a low day count, by itself, ends your tax residency anywhere.
This guide explains how the day count works in several major countries, what the other tests look at, and why people who move often still need a clear answer to one question: where am I tax resident?
Key takeaways
- Many countries treat roughly 183 days of presence as enough to make you tax resident, but very few treat fewer than 183 days as proof that you are not.
- Countries count days differently: by calendar year, by tax year, over any 12-month period, as a weighted three-year total, or as one continuous stay.
- Home, family, work and economic ties can make you resident with far fewer days, as the rules in the UK, Canada, Spain, Germany and Australia show.
- The 183-day clause in tax treaties covers employment income on short assignments. It does not decide where a person lives.
- Accurate day records are the base of any residence position, but they are only one part of it.
Where the 183-day rule comes from
The number is simple arithmetic: 183 days is just over half of a 365-day year. Lawmakers like it because presence for more than half a year is a reasonable sign that someone lives in a place rather than visits it. That is why so many domestic tax codes use it as a bright-line test.
The second source is the treaty network. Most income tax treaties follow the OECD Model Tax Convention. Its Article 15 lets an employee who is resident in one treaty country work in the other country for a short time without becoming taxable there on the salary, if three conditions all hold. The worker is present in the other country for no more than 183 days in any 12-month period that starts or ends in the tax year concerned. The employer is not resident in that other country. And the pay is not borne by a permanent establishment the employer has there.
This treaty test is narrow. It applies only to employment income, and only to someone who is already a treaty resident of one of the two countries. It is a rule about who taxes a salary, not a rule about where a person lives. Treaties also vary: some older treaties count 183 days per calendar year instead of any 12-month period.
How major countries count days
The table below shows how the day count works in seven well-known systems, as of October 2026. In every case, the day count sits next to other tests.
| Country | Day-count rule | Period measured | Other tests that can make you resident |
|---|---|---|---|
| United States | At least 31 days this year and 183 weighted days over three years | Calendar year, with a look-back | Green card test; citizens are taxed on worldwide income wherever they live |
| United Kingdom | 183 days or more makes you automatically resident | UK tax year (6 April to 5 April) | Home test, full-time work test, sufficient ties test from as few as 16 days |
| Canada | 183 days or more of sojourning makes you a deemed resident for the whole year | Calendar year | Factual residence based on residential ties |
| Australia | 183 days or more, unless your usual place of abode is overseas and you do not intend to take up residence | Income year (1 July to 30 June) | Resides test and domicile test |
| Spain | More than 183 days; sporadic absences count unless you prove tax residence elsewhere | Calendar year | Center of economic interests; spouse and minor children living in Spain |
| Portugal | More than 183 days | Any 12-month period starting or ending in the year | A dwelling kept as a habitual residence |
| Germany | A continuous stay of more than six months is a habitual abode | One continuous period, short breaks ignored | A dwelling you keep and use (domicile), with no day minimum |
The way each day is counted also differs. The ATO says a part day in Australia counts as a full day, and the Canada Revenue Agency (CRA) also counts any part of a day. The UK generally counts a day when you are in the country at midnight. The IRS substantial presence test excludes some days, such as transit of less than 24 hours between two foreign points.
The US formula in practice
The US test is a weighted sum. You count every day in the current year, one third of the days in the year before, and one sixth of the days in the year before that. The IRS gives the example of 120 days in each of three years: 120 + 40 + 20 = 180, so the person is not resident. At 122 days a year, the same formula gives 122 + 40.67 + 20.33 = 183, and the test is met.
Someone who meets the test may still be treated as a nonresident under the closer connection exception. The IRS conditions are that you were in the US for fewer than 183 days in the current year, kept a tax home in a foreign country for the whole year, had a closer connection to that country, had no pending green card application, and filed Form 8840 on time.
Why fewer than 183 days does not end residency
Most of the confusion comes from reading the 183-day test backward. A country may say "183 days makes you resident." That does not mean "fewer than 183 days makes you nonresident." Several common rules work with far fewer days.
The UK can treat you as resident from 16 days
The UK Statutory Residence Test starts with automatic tests and then moves to a sufficient ties test. According to HMRC's RDR3 guidance, someone who was UK resident in any of the previous three tax years needs fewer than 16 days in the UK to be automatically nonresident. Between 16 and 45 days, four ties are enough to make that person resident. The ties cover family, available accommodation, UK work, more than 90 days in either of the previous two years, and whether the UK is where you spent the most midnights. Our UK Statutory Residence Test guide walks through each one.
Canada and Australia look at the whole picture
The CRA's residency folio says a dwelling, a spouse or common-law partner, and dependants in Canada are significant residential ties. It also says that if a person leaves but does not build significant ties abroad, the remaining Canadian ties may take on greater significance, and the person may continue to be resident. No day count is involved in that analysis.
Australia's main test is the resides test, which looks at factors such as family, work, assets and living arrangements. A separate domicile test treats someone whose domicile is in Australia as resident unless the Australian Taxation Office is satisfied that their permanent place of abode is outside Australia. A person who keeps moving may find that hard to show.
Germany and Spain do not need a day count at all
Under German law, keeping a dwelling in circumstances that suggest you will keep and use it is enough for domicile, and domicile alone gives full tax liability. The six-month rule in section 9 of the German Fiscal Code is only a second route in. Spain treats a person as resident if the main base of their business or economic interests is in Spain, or, as a rebuttable presumption, if their spouse and minor children live there.
Citizenship can matter more than days
The United States taxes its citizens on worldwide income no matter where they live. For an American abroad, the day count decides how other countries see them, but not whether the US does. Our guide to citizenship-based taxation explains how this works.
When the day count works against you
The 183-day rule can also surprise people in the other direction. A long stay in a country you think of as a base for travel can make you resident there under domestic law, whether or not you meant to move. Portugal, for example, counts more than 183 days in any rolling 12-month period, so a stay that spans two calendar years can still meet the test.
If two countries both treat you as resident, a tax treaty between them may settle the conflict. Treaties use a fixed order of tests: permanent home, center of vital interests, habitual abode, then nationality. Day counts matter mainly at the habitual abode step. Our article on tax treaty tie-breaker rules covers each step, and our guide to tax residency ties explains what authorities look at before a treaty is ever needed.
Without a treaty, both countries may tax you under their own rules, and relief then depends on each country's foreign tax credit rules.
How a clean day record helps
Even though days are not the whole story, they are the one part of a residence position that is pure fact. Tax authorities can check entry and exit data, flight records, card payments and phone data. The EU's Entry/Exit System now records border crossings of non-EU travelers at Schengen borders electronically, which makes it easier for officials to reconstruct a stay.
A good record usually includes the date and place of each entry and exit, the counting convention each relevant country uses, and backup evidence such as boarding passes and accommodation receipts. Our free day counter and our guide on how to track days for tax residency show one way to keep this organized.
Frequently asked questions
Does the 183-day rule apply in every country?
No. Many countries use a test close to 183 days, but the details differ, and some countries use other periods. Germany, for example, uses a continuous stay of more than six months. Each country's own law decides.
If I spend fewer than 183 days in every country, am I tax resident nowhere?
Not necessarily. Your former country may still treat you as resident through home, family or economic ties, or through special rules for people who leave. Countries such as the US also tax citizens regardless of residence. Being under 183 days everywhere does not on its own prove nonresidence anywhere.
Is the 183-day period always a calendar year?
No. The US and Spain use the calendar year, the UK uses a tax year that runs from 6 April, Australia uses an income year from 1 July, and Portugal uses any 12-month period that starts or ends in the year. Treaty employment clauses often use any 12-month period.
Do partial days count toward 183 days?
It depends on the country. Australia and Canada generally count any part of a day. The UK generally counts days on which you are present at midnight, with some exceptions. The US excludes some days, such as short transits between two foreign points.
What happens if two countries both say I am resident?
If a tax treaty applies, its tie-breaker rules usually assign residence to one country for treaty purposes. If there is no treaty, both countries may tax you, and relief depends on their domestic foreign tax credit rules. People in this position often ask an adviser in each country.
Important: This article is general information, not tax, legal or financial advice. Rules change often and depend on your personal circumstances. Speak with a qualified professional in each relevant country before you act.