Count your days: the Substantial Presence Test.
This year's US days, plus one-third of last year's, plus one-sixth of the year before. At 183, the IRS treats you as resident and taxes your worldwide income.
Figures on this page are stated for tax year 2025/26 UK · 2025 US. Thresholds change annually.
Run the arithmetic
Take your current-year days (31 minimum for the test to apply at all), add a third of last year's and a sixth of the prior year's. Arrival and departure days count as whole days — but a connection through JFK does not, provided you are in the US under 24 hours between two places outside it. Around 122 days a year, sustained across three years, crosses the line.
Over the line isn't the end: the closer-connection exception (Form 8840) or the treaty tie-breaker (Form 8833) can preserve non-resident treatment — but only if claimed, on time, on the right form.
- Formula: days + ⅓ prior year + ⅙ year before
- 183 total triggers residence; arrival and departure days count in full
- Exceptions exist but require forms, not just facts
Count your days, weighted across three years
A quick orientation, not advice — real positions have edges this cannot see.
Enter your current-year days to see the result.
Questions we get about this
Mostly yes - any day you are physically present in the US counts, including arrival and departure days.
The exception worth knowing is transit: under 24 hours in the US while travelling between two places outside it does not count at all. Medical and exempt-visa situations are also excluded, and the count here does not model those.
Treat it as a starting point. If it says an obligation applies, the next question is what the filing actually involves and whether earlier years are affected.
If it says nothing applies, it is worth re-running whenever your circumstances change - a move, a property, a new account.
It weights three years: all days in the current year, a third of the previous year, and a sixth of the year before that.
Meeting the threshold generally makes you a US tax resident for the year, regardless of visa status.
Yes. The closer connection exception and certain visa categories can override the count, and treaty tie-breaker rules may apply on top.
Those exceptions have to be claimed, and some require their own filing.
It covers the common cases and will tell you reliably whether the basics apply to you. It is a guide, not a filing position.
Edge cases - trusts, business ownership, unusual residence patterns - can change the answer, which is why the result flags when a position is worth checking properly.
Related pages
- Free tool
UK statutory residence test
Work through the UK statutory residence test: the automatic tests, the sufficient ties, and the day counts that decide which side of the line you sit.
- Glossary
Substantial Presence Test: definition
The day-count formula that makes visitors into US tax residents.
- Service
183-day US residence status
The US 183-day rule explained: the substantial presence test formula, exempt individuals, the closer connection exception and the treaty tie-breaker.
- Pillar guide
Tax specialists for US and UK
What US and UK tax specialists handle that a general accountant does not: residence tests, treaty relief, FBAR, PFICs, pensions, property and catch-up filings.
- Pillar guide
Accountants for US and UK
How to choose accountants for US and UK tax: what each credential permits, how to verify it, what drives the fee, and when you do not need a specialist.
- Service
Streamlined catch-up filing
Streamlined Foreign Offshore Procedures: 3 years of returns, 6 years of FBARs and the non-wilful certification, with no penalty on the Foreign route.
Further reading
- The statutory residence test in the year you move
Arrival and departure years are where the test bites hardest, and where Americans get it wrong most often. Here is how the three stages actually run.
- Do you need to file a US tax return from abroad?
Owing nothing is not the same as not filing. The duty follows citizenship, the thresholds are lower than people assume, and some forms apply regardless of income.
Last reviewed · Figures stated for tax year 2025/26 UK · 2025 US. Thresholds and rates change annually — check figures against the current tax year before relying on them.
Got your answer and it looks complicated?
These tools are deliberately simple, and real positions rarely are. Send us what you found and we will confirm it properly.