What the tie-breaker rule does
Each country first applies its own tax residency rules, and only when 2 of them say yes for the same period, and a treaty links them, does the treaty's residence article step in. Under Article 4(1) of the OECD Model Tax Convention, you count as resident of a country whose law makes you liable to tax there by reason of domicile, residence or a similar test, not of one that taxes you only on local income.
The result holds for the treaty, and only for the period of dual residence, which can be part of a year (paragraph 10 of the Commentary on Article 4). The winner taxes you as a resident; the loser keeps only what the treaty lets a source country tax, such as pay for work done there, so a dual tax resident usually still files in both countries for that year.
The tie-breaker for individuals under Article 4(2) of the OECD Model. The evidence column follows the Commentary on Article 4.
| Test | You reach it when | It picks the country where | Evidence that carries it |
|---|---|---|---|
| 1. Permanent home | Always the first test | A home is available to you at all times, if only 1 country has one | Lease or deed; proof the other home was sold or rented out to an unrelated tenant |
| 2. Center of vital interests | You have a permanent home in both | Your personal and economic relations are closer | Where your partner and children live, where you work and manage your money |
| 3. Habitual abode | Test 2 gives no answer, or you have a home in neither | You are customarily present, if in 1 country only | Years of travel history: how often, how long, how regularly |
| 4. Nationality | You have a habitual abode in both or in neither | You are a citizen, if of 1 country only | Passports |
| 5. Mutual agreement | You are a citizen of both or of neither | The 2 tax authorities agree | A case presented under Article 25 |
Test 1: a permanent home available to you
If only 1 country has a permanent home available to you, it wins and the later tests are never reached. The OECD expects this to settle many cases on its own, such as someone with a home in 1 country who has only made a stay of some length in the other (paragraph 11 of the Commentary on Article 4, OECD Model).
Any form of home counts: a house or apartment you own or rent, even a rented furnished room. What matters is permanence: the home must be arranged for your permanent use and available at all times, not taken for a stay that is bound to be short, such as a vacation, a business trip or a course (paragraphs 12 and 13). A house you own stops counting while it is rented out and handed over to an unrelated tenant, because you no longer have possession of it (paragraph 13).
Worked example: you sign a 2-year lease on a Lisbon apartment, then a client project keeps you in Madrid for 200 days of 2026 in serviced apartments booked month by month. Spain treats you as resident for spending more than 183 days there in the calendar year (LIRPF, article 9), and Portugal for having a home you appear to intend to keep as your habitual residence (CIRS, article 16). Under a treaty worded like the OECD Model, only Portugal has a permanent home, so Portugal wins at test 1.
Permanent home or not, under the OECD Commentary
Counts as a permanent home
An apartment on a 12-month lease that stays yours while you travel; a furnished room you rent all year; your own house, kept empty, that you can move back into on any day.
Does not count
A hotel or a short-term rental booked for a 3-month project; a place taken for 1 vacation; your house rented out to an unrelated tenant on a 2-year lease, even though you still own it.
Test 2: center of vital interests
With a permanent home in both countries, the treaty asks which one your personal and economic relations are closer to. The Commentary lists your family and social relations, occupation, political, cultural or other activities, place of business and the place you manage your property from, examined as a whole, with special attention to your own personal acts (paragraph 15, OECD Model). It adds that keeping your first home, where you have always lived and where your family and possessions are, can show your center of vital interests never left.
Worked example: you rent in Dubai and spend 200 days of the year there, which passes the UAE test of 183 days or more in 12 consecutive months (Cabinet Decision No. 85 of 2022, article 4). You keep the London house, where your partner and 2 children stay for school, and with 120 days in the UK plus a family tie and an accommodation tie, the UK still treats you as resident (HMRC RDR3, sufficient ties test). Your family and lifelong base pull toward the UK despite fewer days there; move the family, bank and advisers to Dubai, and the same 200 days point the other way.
A real case: Oppenheimer v HMRC
Jonathan Oppenheimer, a South African national, moved to the UK with his family on August 1, 2007. HMRC assessed £10,119,586 (about $13,400,000) of extra tax on £20,159,139 (about $26,700,000) of trust remittances for 5 tax years between 2010/11 and 2016/17, on the basis that he was treaty resident in the UK (First-tier Tribunal, Oppenheimer v HMRC).
He did not dispute being UK resident under the UK's own rules, including the statutory residence test from 2014/15, and he had a permanent home in both countries. HMRC leaned on his wife and children living in the UK and on the time he spent and worked there. The tribunal called the family a key relationship but not the only one: it accepted he worked from the UK more than anywhere else, but found his occupations, friendships and politics tied to South Africa, where he voted (never in the UK) and kept his principal doctor and dentist.
It held that throughout the period his personal and economic relations were closer to South Africa, and that even if they were not, he had a habitual abode in both countries, so nationality would have sent him to South Africa anyway. The appeal succeeded on March 24, 2022.
- UK
- South Africa
- Elsewhere
Source: First-tier Tribunal, Oppenheimer v HMRC [2022] UKFTT 00112 (TC), paragraph 200 The tribunal printed 2009/10 and 2012/13 for context; they sit outside the years under appeal. More days in the UK than in South Africa every year, and treaty residence in South Africa all the same.
Show the numbers
| UK | South Africa | Elsewhere | Total | |
|---|---|---|---|---|
| 2009/10 | 191 days | 121 days | 70 days | 382 days |
| 2010/11 | 188 days | 126 days | 68 days | 382 days |
| 2011/12 | 185 days | 74 days | 116 days | 375 days |
| 2012/13 | 197 days | 67 days | 132 days | 396 days |
Test 3: habitual abode, which is not a day count
Habitual abode decides 2 cases: you have a home in both countries and no clear center of vital interests, or you have a home in neither, like a person going from 1 hotel to another (paragraphs 16 to 18 of the Commentary on Article 4, OECD Model). That is the exposure in the perpetual traveler plan: if 2 countries do claim you and you hold a home in neither, the case goes straight to habitual abode, and your travel pattern decides it.
The larger day count alone does not win. The test asks whether you were customarily present in 1 country but not the other, judged by the frequency, duration and regularity of stays that form the settled routine of your life (paragraph 19). Over 5 years, someone who works in State A and returns to State B 2 days a month plus a 3-week vacation a year has a habitual abode in A only; someone who returns to A 15 times a year for 2 weeks and spends the rest of the time in B has one in both.
The period examined can be longer than the dual residence itself: a worker who spends 190 days in State D with a permanent home in neither country, then returns home to State C for good, is judged on the routine of the years before as well (paragraph 19.1). So your day log does 2 jobs. Keep it the way each country counts days for tax residency, arrival and departure days included, and keep it for several years.
Winning the day count does not win the tie-breaker
Extra days in the country you want to win make you resident there under its own law, not under the treaty. Spend 220 days in a Valencia apartment rented by the year while your Berlin apartment stays furnished for your visits, and Germany still counts you as resident through that home (§ 8 AO). Both countries then have a permanent home, so the case goes to test 2, where your family, clients and bank weigh more than the 220 days. Plan where your home, family and business sit; a calendar alone will not carry the case.
Tests 4 and 5: nationality, then the tax authorities
With a habitual abode in both countries or in neither, citizenship decides, if you hold the citizenship of 1 of the 2 and not the other (Article 4(2)(c), OECD Model). A citizen of both, or of neither, goes to the competent authorities of the 2 countries, who settle it by mutual agreement. You present the case to either authority within 3 years of the first notification of the action that taxes you against the treaty (OECD Model, Article 25(1)).
The 2016 US Model keeps the same 5 tests in the same order, but says the authorities shall endeavor to settle the question, a promise to try rather than a promise of an answer (US Model, Article 4(3)).
Worked example: a Canadian citizen keeps apartments in Lisbon and Madrid, splits her work and friends between them and moves between the 2 every few weeks, ending 2026 with 190 days in Spain. Spain claims her for more than 183 days in the calendar year (LIRPF, article 9), Portugal for a home she keeps as her habitual residence (CIRS, article 16), and with a settled routine in each she has a habitual abode in both. She is a national of neither, so under a treaty worded like the Model the 2 tax authorities decide. A Portuguese citizen with the same facts would be resident of Portugal at test 4.
The tie-breaker for companies: Article 4(3)
A company can be resident in 2 countries too, typically when 1 taxes it because it is registered there and the other because it is managed there (paragraph 21 of the Commentary on Article 4, OECD Model). For a founder running a 1-person company from a laptop, the second country is usually wherever the decisions get made, so the company's place of effective management is the fact to pin down first.
Since 2017 the OECD Model has no automatic answer. The 2 competent authorities try to agree on a single residence, having regard to the place of effective management, the place of incorporation and other relevant factors, and until they agree the company gets no treaty relief except as they allow (Article 4(3)). The listed factors include where the board meets, where senior management works, and where the headquarters and accounting records are (paragraph 24.1).
Without an agreement the company stays resident of both countries for other purposes, so an employee working in the other country loses the treaty's 183-day salary exemption, which requires an employer not resident there (OECD Model, Commentary on Article 4, paragraph 24.4). The request goes through Article 25 within 3 years of the first notice that relief was denied (paragraph 24.2).
Many treaties signed before 2017 keep the older rule, under which a dual-resident company is resident only where its place of effective management is: HMRC says the UK uses it as the tie-breaker in many of its treaties (HMRC INTM120085), and paragraph 24.5 still offers it to countries that prefer it. The Multilateral Instrument replaced it with the competent-authority test in the older treaties it covers, unless either country reserved against its Article 4 (MLI, Article 4), so read your treaty as the MLI modified it. The 2016 US Model takes a third line: a company resident in both countries is treated as resident of neither when it claims treaty benefits (US Model, Article 4(4)).
Canada: losing the tie-breaker makes you a non-resident
Canada carries the treaty result all the way into its own law: an individual resident in Canada who is resident of another country under a tax treaty is deemed a non-resident of Canada for all purposes of its Income Tax Act (CRA, Income Tax Folio S5-F1-C1).
Losing the tie-breaker is therefore a departure. The rules for emigrants apply from that date, including the deemed disposition of certain property behind Canada's departure tax, even if you kept your Canadian home. The CRA also puts the burden on you to show you are liable to tax in the other country.
How to build your tie-breaker evidence
Every test is a question of fact decided on records, and the burden usually sits with you: in Oppenheimer the taxpayer had to prove his case for each year in dispute. A tax residency certificate from the country you claim helps, but it shows only that 1 country treats you as resident; the other can still argue the tie-breaker.
Your evidence file for a tie-breaker claim
- Test 1: the lease or deed for the home you claim, and for any home in the other country, the sale contract or the lease to an unrelated tenant.
- Test 2: where your partner and children live and study, where you work and who your clients are, where your bank and advisers are, and where you vote and see your doctor.
- Test 3: a day log with flights, arrival and departure days, covering several years, not only the year in dispute.
- Test 4: your passports, and the date you acquired each citizenship.
- A tax residency certificate from the country you claim, for each year.
- The residence article of the actual treaty between your 2 countries, since its wording can differ from the OECD Model.
David's note
The only test you fully control is the first one. Keep a home in both countries and the case moves to center of vital interests, where the country you left starts with your history, your possessions and often your family. If you are leaving for good, I would sell the old home or rent it out to an unrelated tenant on a long lease before the new tax year starts, and make sure the home you claim is yours all year, not booked trip by trip.
