When someone is resident in both countries under each country's own law, Article 4(4) of the US-UK income tax treaty (opens the official IRS page in a new tab) assigns them to one, using four tests in a fixed order. A non-citizen assigned to the UK files Form 1040-NR with Form 8833. A US citizen remains taxable by the US whatever the result.
This post is for British nationals and other non-citizens caught by both the US day count and the UK residence test, and for anyone holding a green card. It takes one paragraph of our guide to avoiding US-UK double taxation and turns it into a working ladder, with a worked example and the things a successful claim leaves untouched.
When does the US-UK treaty tie-breaker apply
Only after both domestic tests say yes. Article 4(4) applies where an individual is resident in both countries under Article 4(1), which borrows each country's own law. Someone resident in just one of them under domestic rules is resident there for the treaty, and never reaches the ladder.
On the US side, a non-citizen is caught by the green card test or the substantial presence test (opens the official IRS page in a new tab): at least 31 days in the current year and a weighted total of 183 days, counting all current-year days, a third of the prior year and a sixth of the year before. Days as an exempt individual and transit days under 24 hours between two foreign places fall out.
On the UK side, the Statutory Residence Test (opens the official HMRC page in a new tab) works through automatic overseas tests, automatic UK tests and then sufficient ties. It is a different test, measured over a tax year from 6 April, so the two periods overlap without matching. The closer connection exception (opens the official IRS page in a new tab) should be checked first, because it is a separate domestic route on Form 8840. It needs fewer than 183 days of US presence in the year, a foreign tax home for the whole year and no green card steps under way.
- Below the US tests: no US residence, no tie-breaker needed
- Caught by the US count but eligible for closer connection: consider Form 8840 first
- Too many US days for that exception and UK resident under the SRT: go to Article 4
- Not UK resident under the SRT: US resident only, no ladder to climb
How does the Article 4 ladder decide residence
Work down the rungs in order and stop at the first that gives one country. A home available in only one country ends the enquiry there, however many days are spent elsewhere. Day counts, which created the conflict, carry no weight until the habitual abode rung, and even then they are only part of the picture.
The first rung asks about availability, not ownership. HMRC's helpsheet HS302 on dual residents (opens the official HMRC page in a new tab) describes accommodation always available for personal use. A family house that has been let on a long tenancy may fail that description, and a leased apartment held all year may meet it. The second rung weighs personal and economic relations together.
HMRC's manual on dual residents (opens the official HMRC page in a new tab) says a claim to treaty residence elsewhere is not accepted uncritically and that the facts behind it need assembling. Keep the lease, the family's addresses, a day log and a note of why each rung was decided as it was. Facts change, and Form 8833 is required annually, so run the ladder afresh for each year.
- Permanent home available in one country only: resident there, stop
- Home in both: resident where personal and economic relations are closer, if that can be determined
- Vital interests unclear, or no home in either: resident where the habitual abode is
- Habitual abode in both or neither: resident in the country of nationality
- National of both or neither: the competent authorities try to settle it by mutual agreement
How does the ladder work for a seconded employee
Take a British national employed by a Leeds engineering company and seconded to Houston for a calendar year, spending 200 days there and 165 in England. Her spouse and two children stay in the family house in Leeds. She leases a Houston apartment for the full year. The ladder puts her in the UK.
The 200 days pass the US test and rule out closer connection, which stops short of 183 days. We assume she meets no automatic overseas test and that her family, accommodation and UK days make her UK resident on sufficient ties. She has a home in each country, which clears the first rung without an answer. Her spouse, children, house, pension and long-term employer are all in England, so the second rung gives the UK, and she stops there.
She files Form 1040-NR with Form 8833. The treaty protection for short visits in Article 14(2) is unavailable, because her Houston stay exceeds its day limit, so the US taxes the pay for work done there. The UK taxes her worldwide income and gives relief for the US tax. Change one fact: if the family moves to Houston and the Leeds house is let and no longer available to her, the first rung may give the US alone. She would then file Form 1040 and look to HS302 for relief from UK tax.
What does a Form 1040-NR claim change on the US return
The claim changes how US income tax is worked out and little else. Publication 519 (opens the official IRS page in a new tab) says a non-citizen who claims residence in the other country under a tie-breaker figures tax as a nonresident alien, and for other purposes remains a US resident. The return taxes US income, not worldwide income.
The mechanics come from the Form 8833 (opens the official IRS page in a new tab) instructions and Regulation 301.7701(b)-7. The dual-resident box is ticked on the form, which goes with a Form 1040-NR (opens the official IRS page in a new tab) filed by the due date for nonresident returns, including extensions. Publication 519 rules out the standard deduction, and the regulation's examples show a joint return lost and mortgage interest on a personal residence no longer deductible. Our Form 8833 post sets out how disclosure works across other treaty positions.
The residual US residence is where people get caught. The Treasury's technical explanation (opens the official US Treasury page in a new tab) gives the controlled foreign corporation example: shares held by the claimant still count as held by a US resident, which can turn other shareholders into United States shareholders. The FBAR manual (opens the official IRS page in a new tab) says treaty provisions do not affect residency for FBAR purposes, so foreign accounts above $10,000 in aggregate stay reportable to FinCEN. Form 8938 is treated differently: the instructions (opens the official IRS page in a new tab) relieve the period on Form 1040-NR, provided the regulation's filing conditions are met.
- Changes: tax figured as a nonresident alien for the dual-resident part of the year
- Changes: no joint return and no standard deduction
- Stays: FBAR, filed with FinCEN and separate from the return
- Stays: US resident status when counting shareholders of a foreign corporation
- Conditional: Form 8938 relief, only with timely Form 1040-NR and Form 8833
What changes for a US citizen who is dual resident
A citizen can be placed on the ladder but cannot use the result to leave US tax. The saving clause in Article 1(4) lets the US tax its citizens as if the treaty had not come into effect. Form 8833 confines the dual-resident route to alien individuals, so a citizen files Form 1040 on worldwide income.
A citizen counts as a US resident for the treaty only with a substantial presence, permanent home or habitual abode in the US. The technical explanation says that a citizen failing that condition is still taxable on worldwide income under the Code. The ladder result only changes who may claim what under the treaty, and our post on the saving clause lists the benefits that survive.
The rungs can still matter on the UK side. A citizen living in New York who is UK resident under the SRT, perhaps because of a long UK project, may be assigned to the US by the ladder. HS302 then allows a claim for relief from UK tax on items such as interest, royalties and UK dividends, where the treaty gives it. A citizen assigned to the UK pays UK tax on worldwide income and uses the foreign tax credit (opens the official IRS page in a new tab) on the US return in the normal way.
Why is the tie-breaker a trap for green card holders
Because the claim that lowers this year's US tax can end US residence altogether. Form 8833 warns that a dual-resident long-term resident who elects treaty residence abroad is deemed to have expatriated under section 877A, and must file Form 8854. Short-term holders avoid that result but carry other risks.
A long-term resident is someone who held the card in at least eight of the last fifteen tax years. The Form 8854 instructions (opens the official IRS page in a new tab) treat the expatriation date as the date treaty residence began, with notice given to the IRS, if treaty benefits were not waived. A covered expatriate is then tested on net worth of $2 million, average annual net income tax above $206,000 for 2025 expatriations, and failure to certify five years of compliance. Failing the certification alone is enough, whatever the person's wealth, and the expatriation tax (opens the official IRS page in a new tab) follows.
The count works in a useful direction for a short-held card. A year in which the holder was treated as a treaty resident abroad, without waiving benefits, is excluded from the eight. Immigration is a separate question, and the regulation warns that filing Form 1040-NR may affect whether the card can be kept. USCIS lists declaring yourself a nonimmigrant on a US tax return among acts that can amount to abandonment. Our renunciation and expatriation service models the position before any claim is signed.
- Count the tax years the card has been held, including the current one
- Check whether any earlier year was already filed on a treaty claim
- Test the net worth, tax liability and five-year compliance conditions
- Take immigration advice on keeping the card before filing Form 1040-NR
- Remember that the green card test (opens the official IRS page in a new tab) applies until status formally ends
What happens on the UK return after a tie-breaker claim
Treaty residence does not remove UK domestic residence. HMRC's manual says UK returns and related obligations may still apply to someone who is treaty resident abroad. A person assigned to the US reports on SA109 and claims relief with the HS302 form; a person assigned to the UK stays taxable on worldwide income, subject to the new-arrivals regime.
The SA109 pages must be filed by commercial software or on paper, because HMRC's free online service does not take them, and the online deadline of 31 January is unchanged. The SA109 form (opens the official HMRC page in a new tab) notes point dual residents to Helpsheet 302 where relief is claimed. HS302 says a person living in the US does not need a certificate of overseas residence. Employment exercised in the UK can still be taxed there under Article 14.
Keep the two returns consistent. A Form 1040-NR saying Leeds is the centre of vital interests and an SA109 claiming Houston is a contradiction that either authority can find. Our treaty relief service records the ladder reasoning once and uses it on both returns. The wider set of reliefs is in the guide to US-UK double taxation.
General information, not advice. The right answer depends on your circumstances and the tax year concerned.
