Cross-Border · Tax Residency Calculator

Tax Residency Calculator: Where Do You Owe Tax?

Your tax home isn't where you say you live — it's where the rules say you do. Move the sliders to see how your days across the US, UK and UAE decide your residency, and the catches most people never see coming.

Days you spend per year in each country
🇺🇸
United States
120
days / year
—
🇬🇧
United Kingdom
90
days / year
—
🇦🇪
UAE · Dubai
155
days / year
—

A simplified simulation for guidance only — real residency tests weigh ties, prior years and treaties. Not advice.

US Substantial Presence Test Calculator

The US test is not a simple 183-day count. It looks back over three years and weights them: every day this year counts in full, days last year count as one third, and days the year before count as one sixth. Enter your day counts to see where you land.

Indicative only. Certain days are excluded from the count — days as an exempt individual, some days you were unable to leave for medical reasons, and days as a regular commuter from Canada or Mexico among them. A closer connection claim or a treaty tie-breaker can also change the result. Confirm your position against the IRS substantial presence test guidance and take advice before relying on it.

The 183-Day Rule Is Not One Rule

Almost everyone arrives at this question having heard that 183 days decides tax residency. The number is real, but it belongs to several different tests that work in genuinely different ways — and assuming they behave alike is how people end up resident somewhere they did not expect.

In the United States, 183 is a weighted total across three years rather than a count of this year's days. In the United Kingdom, 183 days is one of several automatic tests, and you can be UK resident on far fewer days once your ties are counted. In the UAE, day counts sit alongside other conditions. Three countries, three meanings, one number.

How the US Substantial Presence Test Works

The substantial presence test asks two things, and both must be true. First, were you present in the United States on at least 31 days during the current year. Second, does the weighted three-year total reach 183 days, counting all of this year's days, one third of last year's, and one sixth of the year before that.

The consequence catches frequent travellers. Someone spending around 120 days a year in the US every year — a pattern that never approaches 183 in any single year — reaches roughly 180 on the weighted formula and sits on the edge of US residency. The calculator above does that arithmetic for you.

Two important qualifications. Not every day counts: the rules exclude days for certain categories of person and certain circumstances. And even where the test is met, a closer connection claim or a treaty tie-breaker may still leave you taxed as a non-resident. Those are documented positions, not assumptions — they have to be claimed properly.

One group can ignore the test entirely, and not in a good way. US citizens and green-card holders are taxed on worldwide income wherever they live, regardless of days. If that is you, the day count changes nothing about your filing obligation. Our guide for the Accidental American covers what that means for someone who never chose the citizenship.

How the UK Statutory Residence Test Works

The UK test runs in a fixed order, and you stop at the first part that gives an answer. The automatic overseas tests come first and can make you non-resident on a low day count. The automatic UK tests come next — spending 183 days or more in the UK in the tax year makes you resident, as can having your only home in the UK or working full-time here. Only if neither set settles the question do you reach the sufficient ties test.

The ties test is where day counts stop being decisive on their own. It pairs your UK days with the number of connections you have to the UK — family here, available accommodation, substantive UK work, ninety days or more in the UK in either of the two previous tax years, and for those leaving, whether the UK is where you spend most days. The more ties you have, the fewer days it takes to make you resident, and the thresholds differ depending on whether you were UK resident in any of the previous three tax years.

Because those bands are precise, and because HMRC itself revised the ties-test day figures during 2026 to align its guidance with the legislation, we deliberately do not reproduce a table here that could go stale between updates. The authoritative statement is HMRC's Residence and FIG Regime Manual, with the plain-English version in RDR3 and a summary on tax on foreign income. The UK tax year runs 6 April to 5 April, which is itself a common source of miscounting for anyone used to a calendar year.

Two boundaries are worth knowing before you start counting. If you were UK resident in any of the previous three tax years and spend fewer than 16 days here, you are automatically non-resident and never reach the ties test at all. If you were not UK resident in any of those three years, the same is true below 46 days. The ties test only does work in the range between those floors and the automatic 183-day ceiling.

When Two Countries Both Say You Are Resident

Dual residence is common and is not, by itself, a disaster. Where a double tax treaty exists, it contains a tie-breaker that assigns residence to one country for treaty purposes — looking in turn at where you have a permanent home available, where your personal and economic ties are strongest, where you habitually live, and then nationality.

The trap is assuming a treaty is always there. The US and the UAE have no income tax treaty, so someone caught by both systems has no tie-breaker to fall back on and relief depends on foreign tax credits alone. That single fact reshapes a great many Dubai relocation plans, and it is worth establishing before you move rather than afterwards.

If your position is genuinely borderline, the honest answer is that day-count tools cannot resolve it. Residency turns on facts, documents and sometimes a treaty claim that has to be made on a return. Our US and UK expat tax service covers exactly this work, and you can book a confidential consultation to have your own facts looked at.

What this calculator does not model

This is an indicative day-count tool, not a residency determination. It does not model split-year treatment, exceptional circumstances, the deeming rule, temporary non-residence, the full sufficient-hours-of-work computation, or treaty tie-breakers — and a UK statutory residence outcome does not by itself decide your residence for treaty purposes. Days excluded from the US count, and the definitions behind each UK tie, are matters of fact that change the answer. Anything close to a threshold should be confirmed against the official guidance linked above and reviewed by a licensed professional before you act on it.

FAQ
Asked Most Often

Tax Residency Questions

How do I calculate my tax residency?+
Start by identifying which test applies to each country you spend time in, because they do not work alike. The US substantial presence test weights three years of days; the UK statutory residence test runs automatic overseas tests, then automatic UK tests, then a sufficient ties test that combines days with your connections to the UK. Count days accurately for each country's own tax year, then check the result against that country's official guidance.
What is the 183-day rule?+
It is shorthand for several different rules that share a number. Spending 183 days or more in the UK in a tax year makes you UK resident automatically. In the US, 183 is not this year's day count but a weighted three-year total: all of this year's days, a third of last year's and a sixth of the year before. Treating the two as the same rule is one of the most common and costly residency mistakes.
What is the substantial presence test?+
It is the day-count test that determines whether a non-citizen is treated as a US tax resident. Two conditions must both be met: at least 31 days of US presence in the current year, and a weighted total of at least 183 days across three years, counting current-year days in full, prior-year days as one third, and days from two years ago as one sixth.
How is the substantial presence test calculated?+
Add all your US days this year, plus one third of last year's days, plus one sixth of the days from the year before. If that total reaches 183 and you were present at least 31 days this year, you meet the test. The calculator on this page performs the arithmetic, but note that certain days are excluded from the count and a closer connection claim or treaty tie-breaker can still change the outcome.
Can I be a US tax resident without living in the US?+
Yes, and it happens more often than people expect. Because the substantial presence test weights three years, a repeating pattern of roughly 120 days a year never reaches 183 in any single year yet can cross the threshold on the weighted formula. Frequent business travellers and people with a US holiday home are the usual cases.
Do US citizens need to use the substantial presence test?+
No. US citizens and green-card holders are taxed on their worldwide income wherever they live, so the day count does not determine their filing obligation. The substantial presence test matters for people who are not US citizens or lawful permanent residents. If you hold US citizenship you have a filing duty regardless of how few days you spend there.
Does a green card make me a US tax resident even if I live abroad?+
Yes. Holding a green card is an independent route to US tax residency: a lawful permanent resident is treated as a US resident for federal tax purposes regardless of how many days are spent in the country. The substantial presence test is not reached, because residency is already established. Green-card holders living overseas therefore keep a full US filing obligation on worldwide income until the status is formally given up.
Can I spend more than 183 days in the US and still not be treated as resident?+
Not through the closer connection exception, which is only available if you were present in the United States for fewer than 183 actual days in the year. This is where the two meanings of 183 collide: the substantial presence test uses a weighted three-year total, while the closer connection exception uses your actual current-year days. Above that line, a treaty tie-breaker may still be available depending on the country, but it is a claimed position that has to be made properly on a return.
What is the UK statutory residence test?+
It is the statutory framework that decides UK tax residence for a tax year. It applies in a set order: automatic overseas tests first, which can make you non-resident on a low day count; then automatic UK tests, including spending 183 days or more in the UK; and only if neither resolves the position, the sufficient ties test, which combines your UK days with the number of ties you have to the UK.
How many days can I spend in the UK without becoming tax resident?+
There is no single number, which is exactly why the test exists. The threshold depends on how many ties you have to the UK and on whether you were UK resident in any of the previous three tax years, and someone with several ties can become resident on a far lower day count than someone with none. HMRC's RDR3 guidance sets out the current day bands for each combination.
What counts as a tie under the UK sufficient ties test?+
The ties cover family in the UK, accommodation available to you here, substantive UK work, spending ninety days or more in the UK in either of the two previous tax years, and, for people leaving the UK, whether the UK is the country where you spend the most days. Each has a precise definition, so whether something counts is a question of fact rather than impression.
Does the UK tax year matter when counting days?+
It matters a great deal. The UK tax year runs from 6 April to 5 April, not January to December, so anyone counting days on a calendar year is counting the wrong period. Because the US uses a calendar year, cross-border cases involve two different counting windows over the same travel history.
What happens if I am tax resident in two countries at once?+
Where a double tax treaty exists between them, it contains a tie-breaker that assigns residence to one country for treaty purposes, looking at permanent home, centre of vital interests, habitual abode and then nationality. Where no treaty exists between the two countries, as with the US and the UAE, there is no tie-breaker and relief depends on foreign tax credits instead.
Is this tax residency calculator accurate enough to rely on?+
Treat it as an indication, not a conclusion. It applies the headline day-count arithmetic, but real residency questions turn on excluded days, the precise definition of a tie, treaty positions and your prior-year history. Anything borderline should be confirmed against official guidance and reviewed by a licensed professional before you act on it, because the cost of getting residency wrong is usually a full year of tax in the wrong country.

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