The Substantial Presence Test for UK Citizens Moving to the US

The substantial presence test makes a non-US citizen a US tax resident when they are physically in the United States for at least 31 days in the current year and at least 183 weighted days over three years: every day this year, one third of last year's days and one sixth of the days the year before. It is set out in IRS Publication 519.

For a British citizen on a secondment, a long project or a slow relocation, this test decides whether the IRS taxes only US-source income or worldwide income. It runs on a calendar year and counts part days as whole days. This guide explains how the arithmetic works, which days you can exclude, and how the closer connection exception and the US-UK treaty can switch residency off again.

How the substantial presence test is calculated

The IRS substantial presence test has two limbs, and you must meet both. First, you must be present in the United States on at least 31 days during the current calendar year. Second, the weighted three-year total must reach 183 days.

The 183-day weighted formula

The weighted total counts all days in the current year, plus one third of the days in the first preceding year, plus one sixth of the days in the second preceding year. Any part of a day counts as a full day of presence, so a late-evening arrival at JFK is a US day. The table shows how quickly regular visits add up. The figures are illustrative.

In other words, someone who spends about four months a year in the United States, every year, meets the test in the third year without ever spending half a year there. At 120 days a year the total is 180, and the test is not met. That narrow margin is why we ask clients for a day-by-day travel log rather than an estimate.

Why the 31-day limb matters

The 31-day minimum protects people who were heavily present in earlier years but barely visit now. For example, a UK national who spent 300 days in New York in 2025 and 20 days in 2026 is not a US resident for 2026, because the 31-day limb fails. Consequently, the weighted total is irrelevant for that year.

Days that do not count towards the test

Not every day in the United States is a day of presence. IRS Publication 519 lists categories of excluded days, and most require a claim rather than applying automatically.

Exempt individuals and Form 8843

An "exempt individual" does not count days while in that status. The main groups are students on F, J, M or Q visas, teachers and trainees on J or Q visas, and foreign government-related individuals. Exemptions for students and teachers have time limits, generally five calendar years for students and two out of six years for teachers. You claim the exclusion by filing Form 8843, Statement for Exempt Individuals and Individuals With a Medical Condition.

Transit, medical and commuter days

Furthermore, you do not count days in transit between two foreign points if you are in the United States for less than 24 hours. Days when a medical condition that arose in the United States prevented you from leaving are also excluded, again via Form 8843.

The closer connection exception and Form 8840

Meeting the substantial presence test does not always make you a US resident. The closer connection exception lets you remain a non-resident alien if you were present for fewer than 183 days in the current year, kept a tax home in a foreign country throughout the year, and had a closer connection to that country than to the United States.

What a closer connection means

The IRS looks at where your permanent home, family, personal belongings, bank accounts, driving licence, voter registration and social ties sit. A UK citizen who owns a home in Manchester, has children in a UK school and works for a UK employer usually has a strong case. However, you cannot claim the exception if you have applied for, or taken steps towards, a US green card during the year.

Filing Form 8840 on time

You claim the exception on Form 8840, Closer Connection Exception Statement for Aliens. It is attached to Form 1040-NR or, if no return is required, filed separately by the return due date, which is 15 June for most non-residents without US wages. Importantly, a late or missing Form 8840 can cost you the exception altogether. Therefore, treat it as a deadline, not a formality.

When the US-UK treaty tie-breaker applies

Someone who spends 183 days or more in the United States in the current year cannot use the closer connection exception. Nevertheless, a UK resident in that position may still be treated as non-US resident under Article 4 of the US-UK income tax treaty.

Article 4 and Form 8833

Article 4 of the treaty applies a sequence of tie-breakers for an individual resident in both countries: permanent home, centre of vital interests, habitual abode and, finally, nationality. Our guide to the US-UK treaty tie-breaker rule walks through each step. To rely on the result, you file Form 1040-NR and disclose the position on Form 8833, Treaty-Based Return Position Disclosure. The wider treaty framework is covered on our UK-US tax treaty page.

What a treaty non-resident still owes

A treaty position changes how your income tax is calculated. It does not necessarily remove every other US obligation. For instance, you may still be treated as a US resident for some information-reporting purposes. Accordingly, check foreign account and entity reporting before assuming the treaty has made you invisible to the IRS.

Residency start dates and the dual-status year

If you meet the substantial presence test, your US residency usually starts on the first day you were present in that calendar year, not on 1 January. You are therefore a dual-status taxpayer for the year you arrive: non-resident before that date and resident after it.

The 10-day de minimis rule

You can disregard up to 10 days of presence at the start of the year if you had a closer connection to a foreign country on those days. For example, a house-hunting trip in February before a move in May may not start your residency early. As a result, the residency start date can shift by months, which changes how much UK salary falls into the US-resident period.

The UK and UAE side of the same move

The US test is only half of the picture. HMRC applies the Statutory Residence Test, described in its RDR3 guidance, which uses the 6 April to 5 April tax year and its own day-counting rules. A move to the United States often qualifies for split-year treatment, explained in our guide to split-year treatment when leaving the UK.

Similarly, UAE tax residence for individuals generally requires 183 days of presence in a 12-month period under Cabinet Decision No. 85 of 2022, issued through the UAE Federal Tax Authority. A Briton working between Dubai, London and New York can therefore count three different sets of days in three different periods. Our comparison of the 183-day rule in the UK, US and UAE sets them side by side.

A worked scenario from our practice

A London-based engineer spent 140 days in Texas in 2026 on a project, after 130 days in 2025 and 90 days in 2024. Her weighted total was 140 + 43.33 + 15, or 198.33 days, so she met the substantial presence test. However, she was present for fewer than 183 days in 2026, kept her London home and family, and had no green card application. We filed Form 8840 with Form 1040-NR by 15 June, and she remained a non-resident alien taxed only on her US-source income.

Had she spent 190 days in Texas, Form 8840 would not have been available. Instead, the outcome would have depended on the Article 4 tie-breaker and Form 8833. If you are planning US work days, book a consultation before the calendar year runs away from you. We can map your days against both countries' rules and file the right statements on time. Our team also handles the US expat tax returns that follow.

Frequently Asked Questions

What is the substantial presence test?

The substantial presence test is the IRS rule that makes a non-US citizen a US tax resident by physical presence. You meet it if you are in the United States for at least 31 days in the current year and 183 weighted days over three years, counting all current-year days, one third of last year's days and one sixth of the days two years ago.

Does a part day count under the substantial presence test?

Yes. Under IRS Publication 519, being in the United States for any part of a day generally counts as a full day of presence. The main exception is transit between two foreign points lasting less than 24 hours, which is not counted.

Can a UK citizen spend 182 days in the US without becoming a US tax resident?

Not automatically. A UK citizen can meet the substantial presence test with fewer than 183 days in the current year because of the three-year weighted formula. However, if they were present for fewer than 183 days in the current year, they may avoid US residency by filing Form 8840 to claim the closer connection exception.

What is Form 8840 and when is it due?

Form 8840 is the IRS Closer Connection Exception Statement for Aliens. It is attached to Form 1040-NR or, if no return is required, filed separately by the return due date, which is 15 June for most non-residents without US wages. Filing late can mean losing the exception.

Can the US-UK tax treaty override the substantial presence test?

Yes, for income tax purposes. Article 4 of the US-UK income tax treaty uses tie-breakers such as permanent home and centre of vital interests to decide residence for a person resident in both countries. A taxpayer relying on the treaty files Form 1040-NR and discloses the position on Form 8833.

Does the substantial presence test apply to UAE residents?

Yes. The substantial presence test applies to any non-US citizen regardless of where they live. A UAE resident who spends significant time in the United States can become a US tax resident, and there is no US-UAE income tax treaty tie-breaker to fall back on, so the closer connection exception is often the only relief.