Substantial Presence Test for a UK Citizen: When You Become a US Tax Resident

The substantial presence test makes a UK citizen a US tax resident for a calendar year when they are in the United States on at least 31 days that year and on 183 days over three years, counting all of this year's days, one-third of last year's and one-sixth of the year before. Your visa type does not decide it. Your travel record does.

What is the substantial presence test for a UK citizen?

The substantial presence test is the day-count rule the IRS uses to decide whether someone who is not a US citizen is a US resident for tax purposes. A UK citizen without a green card is a nonresident by default and becomes a resident only by meeting this test. A green card holder is resident under a separate rule that ignores days altogether, covered in our guide for green card holders living abroad.

The IRS sets out the test in two parts, and both must be met for the calendar year in question:

1. You were physically present in the United States on at least 31 days during the current year.
2. You were present on 183 days during the three-year period that includes the current year and the two years before it, counting all the days in the current year, one-third of the days in the first year before, and one-sixth of the days in the second year before.

The IRS's own example uses 120 days in each of 2023, 2024 and 2025. The count for 2025 is 120, plus 40, plus 20, which comes to 180. That person does not meet the substantial presence test for 2025.

A day counts if you are physically in the country at any time during it. Arrival day and departure day are both days of presence. The test uses the calendar year, which is one reason it sits awkwardly beside the UK tax year.

How many days can a UK citizen spend in the US before becoming a tax resident?

A UK citizen with no US days in the two earlier years can spend up to 182 days in the US in a year without meeting the substantial presence test. A UK citizen who visits every year has far less room, because the earlier years carry forward. At a steady pattern, the test is met at 122 days a year.

The table applies the IRS formula to six travel patterns. The weighted totals are arithmetic on the published formula, not IRS figures.

Days this year	Days last year	Days the year before	Weighted total	Test met?
120	120	120	120 + 40 + 20 = 180	No
122	122	122	122 + 40.67 + 20.33 = 183	Yes
150	90	60	150 + 30 + 10 = 190	Yes
100	150	150	100 + 50 + 25 = 175	No
183	0	0	183	Yes
30	300	300	Not reached: fewer than 31 days this year	No

Two practical points follow. The people caught by surprise are rarely those who moved, because they expect to be resident. They are the regular travelers: the consultant with a New York client, the owner of a Florida home who winters there, the partner of a US resident who visits for long stretches. And the count cannot be fixed after the year ends. The only reliable control is a running log of days, kept as the year goes on.

Which days are left out of the count?

The IRS lists a small number of days on which you are not treated as present:

• days you commute to work in the US from a home in Canada or Mexico, if you do so regularly;
• days you are in the US for less than 24 hours in transit between two places outside the United States;
• days you are in the US as a crew member of a foreign vessel;
• days you are unable to leave because of a medical condition that developed while you were in the US;
• days you are an "exempt individual".

"Exempt individual" is a term about day-counting, not about tax. It covers foreign government-related individuals on A or G visas, teachers and trainees on J or Q visas, students on F, J, M or Q visas, and professional athletes temporarily in the US for a charitable sports event. Business visitors, tourists and employees on work visas are not in any of those categories, so their days count from the first one.

The student and teacher categories run out. Publication 519, for 2025, says you will not be an exempt individual as a student if you have been exempt as a teacher, trainee or student for any part of more than 5 calendar years, unless you show that you do not intend to reside permanently in the US and have complied with your visa. A teacher or trainee is generally not exempt if they were exempt as a teacher, trainee or student for any part of 2 of the 6 preceding calendar years.

The exclusion is not automatic. You claim it on Form 8843, attached to your return or, if no return is due, sent to the IRS separately by the return due date. The IRS states that if you do not file Form 8843 on time, you cannot exclude the days, unless you can show by clear and convincing evidence that you took reasonable steps to comply.

The closer connection exception: Form 8840

Meeting the count is not always the end of the matter. Under the closer connection exception, a person who meets the substantial presence test is still treated as a nonresident if they:

• were present in the United States for fewer than 183 days during the year;
• maintained a tax home in a foreign country during the entire year;
• had a closer connection during the year to that one foreign country than to the United States; and
• have not applied for, or taken other steps toward, lawful permanent resident status.

The IRS decides "closer connection" by comparing your contacts with each country. The factors it lists include the country of residence you give on forms and documents, and the location of your permanent home, your family, your personal belongings, your business activities, the jurisdiction where you vote and the jurisdiction that issued your driver's license.

The exception is claimed on Form 8840, attached to a Form 1040-NR or filed alone by the return due date if no return is required. As with Form 8843, late filing generally forfeits the claim. The green card condition is strict: a pending adjustment of status application, or an immigrant petition filed on your behalf, takes the exception off the table.

Illustrative example: a Manchester-based consultant, a UK citizen with no green card, spends 90 days in the US in 2024, 150 days in 2025 and 135 days in 2026 working with clients. For 2026 the count is 135, plus 50, plus 15, which is 200, so the substantial presence test is met. The consultant was in the US for fewer than 183 days in 2026, and their home, family and main place of business stayed in Manchester throughout. Filing Form 8840 on time keeps them a nonresident for 2026.

What if you were in the US for 183 days or more?

At 183 days or more in the current year, the closer connection exception is unavailable, and the US/UK tax treaty becomes the fallback. A UK citizen who meets the substantial presence test and is still UK resident under UK law is resident in both countries. Article 4 of the 2001 UK-USA Double Taxation Convention then applies a series of tie-breaker tests, starting with where the person has a permanent home.

If the tie-breaker points to the UK, Publication 519 says you are treated as a nonresident alien in figuring your US income tax, and you file Form 1040-NR with Form 8833 attached. It also says that for purposes other than figuring your tax, you will be treated as a US resident, which is why foreign account reporting still needs to be checked.

The treaty route leaves more US paperwork in place than the closer connection exception does, and it needs a real UK home to stand on. Our guides to the tie-breaker rule for tax residency and Form 8833 treaty position disclosure go through the tests and the form.

When does US tax residency start and end?

Under the substantial presence test, the IRS says your residency starting date is generally the first day you are present in the United States during the calendar year in which you meet the test. A short trip in January can therefore pull the start of residency back to January, even if the move itself happened in the summer. Publication 519 contains a de minimis rule that can exclude up to 10 days of presence for this purpose, subject to conditions and a signed statement.

A year with a nonresident part and a resident part is a dual-status year. For the resident part, the US taxes worldwide income. For the nonresident part, it taxes only US-source income. The IRS lists restrictions that apply to a dual-status return: no standard deduction, no head of household status, and a joint return only where a dual-status individual married to a US citizen or resident makes the election to file jointly.

At the other end, residency under the substantial presence test generally runs to December 31 of the year you leave. It can end earlier, on your last day of presence, if for the rest of that calendar year you have a tax home in a foreign country and a closer connection to it, and you attach the required statement. Our tax guide for Brits moving to the US covers the arrival-year return and the first-year choice in detail.

What changes once a UK citizen is a US tax resident?

The scope of US tax changes completely. The IRS explains that a nonresident alien is taxed only on US-source income: income effectively connected with a US trade or business at the graduated rates that apply to residents, and other fixed or periodic US income at a flat 30 percent or a lower treaty rate. A resident is taxed on worldwide income.

For a UK citizen that brings the following onto a US return:

• UK salary, rental income, interest and dividends, with a foreign tax credit for UK tax paid on them.
• ISAs. The US does not recognize the wrapper, and funds held inside one can fall under the PFIC rules. See why an ISA is a problem on a US tax return.
• UK bank and investment accounts. A US resident is a US person for FBAR purposes and reports non-US accounts once their combined value exceeds $10,000 at any time in the calendar year. Our guide to FBAR reporting explains the form.
• UK pensions, where the treaty does much of the work.

None of this switches off the UK. HMRC applies its own Statutory Residence Test for the UK tax year, and GOV.UK lists 183 or more days in the UK as only one of several ways to be UK resident. US states also apply their own residency rules, which do not follow the federal test.

What people get wrong about the day count

• "I'm fine as long as I stay under 183 days a year." That is true only for someone with no US days in the two prior years. A regular visitor reaches 183 weighted days at 122 days a year.
• "I'm on a visitor visa, so I can't be a tax resident." Immigration status and tax residency are separate questions. Visitor days count.
• "Travel days don't count." Any part of a day in the US is a day.
• "I pay tax in the UK, so the treaty sorts it out automatically." The treaty position has to be claimed on a Form 1040-NR with Form 8833, and the closer connection exception on Form 8840. Neither applies by default.
• "Students never count days." Student days are excluded for a limited number of calendar years, and only with a timely Form 8843.
• "A green card application doesn't matter until it is approved." Taking steps toward permanent residence removes the closer connection exception for that year.

A routine for keeping the count under control

1. Log every US day as it happens, including arrival and departure days. Keep boarding passes or your travel history as support.
2. Carry forward the two prior years. Start each January knowing one-third of last year's days plus one-sixth of the year before.
3. Work out your ceiling for the year. Subtract that carried-forward figure from 183. The result is the number of days at which the test is met.
4. Check for excluded days and file Form 8843 if you rely on any.
5. If you will meet the test, decide which route applies: the closer connection exception under 183 days, the treaty tie-breaker above it, or resident filing.
6. File the form on time. Forms 8840 and 8843 are both lost by lateness.
7. Review the UK side for the same period, because the UK tax year and the US calendar year overlap rather than match.

Where to get help

US/UK Cross Border Tax is US CPAs and UK tax advisers working as one team, with offices in London, Manchester, New York and San Francisco. We work with UK citizens facing the substantial presence test, from the day count through to treaty relief claims and the US individual tax return that follows.

If your US days are creeping up, or you have already crossed the line for a past year, contact us with your travel dates and we will tell you where you stand in both countries.

Students and scholars on F or J visas are exempt individuals for the test, but only if they file the statement each year; see our guide to Form 8843 for UK students in the US.