Ask a room of internationally mobile people how tax residence works and someone will give the answer with total confidence: stay fewer than 183 days in a country and it cannot tax you. Keep moving, keep every stay under the line, and you are resident nowhere.
The number is real. The rule is not. The 183 days come from a clause in tax treaties about salaries, and where they appear in national law they are usually one test among several, and rarely the one that decides a hard case. The rest of the answer, the part that actually decides where a person lives for tax, is about homes, lives and evidence.
The timing for saying so is good. The OECD has just published the 11th full edition of its Model Tax Convention, the template behind most of the world's tax treaties, containing the text as it read on 18 November 2025. It is the document the 183 days come from. It does not say what the folklore says.
Where the number comes from
The 183 days sit in Article 15 of the OECD Model, the article on income from employment. The general rule is that a salary may be taxed in the country where the work is done. Paragraph 2 makes an exception: the salary is taxable only in the worker's country of residence if the worker is present in the other country for no more than 183 days in any twelve-month period, the employer is not resident there, and the pay is not borne by a permanent establishment the employer has there.
The OECD describes the clause in exactly those terms in the introduction revised by its 2025 update: employment income is taxable in the state where the work is exercised unless the employee is present there for no more than 183 days and certain conditions are met.
Read it again and notice what it is. It is a rule for a person who is already resident somewhere, deciding whether a second country may tax a particular salary. It is not a test of where anyone lives. It says nothing about someone who has no country of residence at all, and it only operates where a treaty exists between the two countries concerned.
What treaties actually ask
Treaties do have a residence rule. It is Article 4, and it contains no day count. Under the OECD Model, a person who is resident in both countries under their domestic laws is treated as resident only where they have a permanent home available to them. If they have a home in both, the question becomes where their personal and economic relations are closer, the centre of vital interests. Only if that cannot be determined, or if there is no permanent home anywhere, does the treaty fall back on habitual abode, then nationality, then negotiation between the two tax authorities.
Two features of this cascade matter. First, it starts with a home and a life, not a calendar. Second, it only applies once both countries have already claimed the person under their own laws. The treaty settles a conflict. It does not create residence and it cannot remove it where no conflict exists.
Domestic law decides first
So the real question is always national law, and national law is far more varied than the folklore allows. Five systems in Asia, the Pacific, the Gulf and Africa show the range.
Japan has no day test at all. The National Tax Agency explains that a resident is an individual who has a domicile in Japan, or who has had a residence there continuously for one year or more. Domicile means the base of a person's life, and it is judged by objective facts. A person can become resident on the day they establish that base.
The UAE, often imagined as a place where residence is a matter of counting days, has three alternative tests in Cabinet Resolution No. 85 of 2022, in force since 1 March 2023. A person is resident if their usual or main place of residence and centre of financial and personal interests are in the UAE; or if they are present for 183 days or more in a relevant twelve-month period; or if they are present for 90 days or more, hold UAE or GCC nationality or a valid UAE residence permit, and either have a permanent place of residence there or work or do business there. Ninety days, not 183, is the line for a resident-permit holder with a home or a job in the country.
New Zealand uses 183 days, but as only one of two doors. Inland Revenue treats someone as resident if they have been in New Zealand for more than 183 days in any twelve-month period, or if they have a permanent place of abode there, meaning a place where they usually live. The way out is narrower than the way in: a resident only becomes non-resident if they have no permanent place of abode in New Zealand and are away for more than 325 days in a twelve-month period.
South Africa looks first at whether someone is ordinarily resident, and only for people who are not does it apply a day test. That test, explained in SARS Interpretation Note 4, counts presence of more than 91 days in the current tax year, more than 91 days in each of the five preceding years, and more than 915 days in total over those five years. Leaving requires a continuous absence of at least 330 full days. And SARS adds that an ordinarily resident person who intends to return remains resident regardless of how long they spend abroad.
Korea comes closest to the folklore, and still does not match it. Its Income Tax Act makes a person resident if they have a domicile in Korea or a place of residence there for 183 days or more. The 183 days are the second limb, not the whole rule. Singapore, similarly, applies 183 days in the previous calendar year to foreigners, but IRAS also treats as resident a foreigner who stays or works there for three consecutive years, even with fewer days in the first and third.
Days count in both directions
Put these systems side by side and the folklore inverts. A day count, where it exists, is a floor for being caught, not a ceiling for being safe. Crossing it makes someone resident; staying under it proves very little. In Japan, a person can be resident with no particular number of days. In New Zealand, a home is enough. In South Africa, an intention to return is enough. In the UAE, 90 days can be enough.
Even the counting itself is less uniform than the folklore assumes. South Africa counts any part of a day as a day, so a traveller who lands five minutes before midnight has spent a day in the country, according to SARS's own example. New Zealand also counts part of a day as a whole one. The UAE looks at a twelve-month period rather than a calendar year, Singapore at the previous calendar year, South Africa at its tax year and the five before it. A person who plans their year around 182 nights in one place and 183 in another has usually counted with the wrong method in at least one of them.
The exits are also asymmetric. Becoming resident is often easy; ceasing to be resident is usually harder, with 325 or 330 days abroad, or a home given up, or a centre of life demonstrably moved. The Brief's piece on Australians filing from abroad showed the same pattern from the other side: leaving a country physically and leaving it for tax are two different events.
The remote worker's version of the myth
The newest form of the folklore concerns remote work: work from anywhere for a few months, and no country cares. The 2025 OECD update did add a number here too. Its new Commentary on Article 5 says that a home or other place used by an individual will generally not be a place of business of their employer if they work there for less than 50% of their total working time over any twelve-month period. At 50% or more, it depends on the facts, with a commercial reason for being in that country as a prominent consideration.
Like Article 15, this is a rule about something else. It decides whether the employer has a taxable presence. It says nothing about whether the worker has become resident, which remains a question for domestic law and, if two countries both claim the worker, for Article 4.
What follows from all this
The 183-day folklore survives because it is easy. It turns a judgment about a life into arithmetic. But every system above asks, in some form, the same questions: where is the home, where is the life, where does the person intend to return, and can they prove it. Counting days answers none of those.
That leads to three conclusions, each argued in earlier Brief pieces. The first is that residence is something you establish with evidence, not something you avoid by moving; the Brief's case for the paper trail is the practical version. The second is that being resident nowhere is not a status any tax authority recognises, which is why flag theory and permanent travel have aged so badly. The third is that a low-tax country is only useful if you actually become resident there, with all the costs that brings, as the Brief set out in zero tax is not zero cost.
Count your days. Every country above counts them too. But plan around a home, a centre of life and a file that proves both, because that is what decides the hard cases.
Work with Sebastian
If you divide your year between countries, or are planning a move and want to know where you will actually be resident for tax before the first day is counted, that is the kind of cross-border planning Sebastian works on with internationally mobile clients. Book a consultation.
