US Substantial Presence Test: Are You a US Tax Resident?

Am I a US tax resident? The short answer

If you are a US citizen or green card holder, you are taxed on worldwide income wherever you live, and no day count changes that. For everyone else, US residency is decided by the Substantial Presence Test.

The test has two conditions and both must be met. You must be present in the United States for at least 31 days in the current calendar year, and your weighted day total across three years must reach 183. The weighting is what makes this test unlike any other in this series: current-year days count in full, the previous year's days count at one third, and the year before that counts at one sixth.

The weighted formula

Written out, the calculation is:

Days this year + (days last year ÷ 3) + (days the year before ÷ 6) ≥ 183

The reason this needs a calculator rather than a rule of thumb is that it rewards intuition poorly. Consider someone who visits the US for four months a year, every year:

That person is a US tax resident, taxable on worldwide income, despite never spending more than a third of any year in the country. Nothing about their travel pattern feels like immigration, and no single year approaches the 183-day figure people tend to have in mind.

The formula is also cumulative in a way that creeps up on people. A pattern that is comfortably below the threshold in its first year can cross it in the third, purely because the earlier years have started contributing.

Days that do not count

Not every day of physical presence counts towards the total. The main exclusions are:

• Days you commute to work from Canada or Mexico on a regular basis
• Days in transit through the US when in transit for less than 24 hours
• Days as a crew member of a foreign vessel
• Days you could not leave because of a medical condition that arose while you were in the US
• Days as an exempt individual

That last category is the most significant. Students on F, J, M or Q visas, teachers and trainees on J or Q visas, and foreign government-related individuals on A or G visas have their days excluded from the count entirely.

The word "exempt" is badly chosen and regularly misunderstood: it means exempt from counting days, not exempt from tax or from filing. Exempt individuals normally still need to file Form 8843 for each year they claim the status.

Exempt status is also time-limited. Students are generally exempt for five calendar years, teachers and trainees for two out of the previous six. The year the exemption runs out is the year people are most often caught unprepared, because days begin counting immediately and the weighted formula can produce residency almost at once.

The Closer Connection Exception

Meeting the Substantial Presence Test does not always make you a resident. The Closer Connection Exception can displace it, but only in defined circumstances and only if actively claimed.

Three conditions must be met. You must have been present in the US for fewer than 183 days in the current year. You must maintain a tax home in another country throughout the year. And you must have a closer connection to that country than to the United States, assessed on factors including the location of your permanent home, family, belongings, social and political ties, and where you hold a driving licence.

Two limitations matter enormously in practice. First, the exception must be claimed by filing Form 8840 by the due date of the return — it is never automatic, and missing the deadline generally forfeits it for that year. Second, it is unavailable if you have applied for, or taken steps to apply for, lawful permanent residence.

The exception also closes hard at 183 current-year days. There is no relief for narrowly exceeding it, which makes the current-year count the binding constraint for anyone relying on this route.

What US residency means

A resident alien is taxable on worldwide income, must file a US return annually, and becomes subject to the full weight of US information reporting.

FBAR (FinCEN Form 114) requires reporting where aggregate foreign account balances exceed 10,000 dollars at any point in the year. FATCA reporting on Form 8938 applies at higher thresholds. Both carry penalties for non-filing that apply independently of whether any tax is owed, which is a structural feature of the US system that has no real UK equivalent.

Where a double tax treaty applies, its tie-breaker provisions may still give the other country the primary taxing right even though you meet the Substantial Presence Test. That outcome is not automatic: it must be claimed as a return position and disclosed on Form 8833, and taking it has consequences of its own, including the fact that treaty-based non-residence does not switch off the information reporting obligations described above. The year you arrive or depart may also be a dual-status year, taxed as part-resident and part-non-resident, which restricts the deductions and filing statuses available to you.

The most damaging surprise for internationally mobile people is usually the PFIC regime. Passive foreign investment company rules apply to most non-US collective investments — including ordinary European funds, many offshore bonds, and a range of pooled products that are entirely mainstream in their home jurisdictions. The US treatment can be punitive, taxing gains at the highest marginal rate with an interest charge for deferral. Structures that are efficient in your country of residence are frequently the ones that produce the worst US outcomes.

Federal residency is not state residency

The Substantial Presence Test determines federal residency only. States apply their own rules, and those rules are often stricter.

Many states combine a domicile test with a statutory day count of their own, and several are notably aggressive in asserting continuing residency over people who have left. It is entirely possible to be a federal non-resident alien while a state continues to treat you as resident and tax your income accordingly. Anyone with a continuing connection to a high-tax state should treat that as a separate analysis rather than assuming the federal answer carries across.

Compliance caveat

US tax positions carry filing penalties that are independent of tax owed, so an incorrect residency assumption is expensive even when no additional tax arises. This tool applies the Substantial Presence Test to the answers you give and shows the weighted arithmetic. It does not address state residency, dual-status years, the first-year choice, treaty tie-breakers, or the expatriation regime under section 877A that can apply to citizens and long-term green card holders who give up their status.

How Global Investments can help

US connections change what good planning looks like, and the interaction between US rules and non-US investment structures is where most avoidable damage occurs. Our advisers work alongside US-qualified specialists to review residency exposure before it crystallises, model the effect of a repeating travel pattern under the weighted formula, and identify holdings that would be treated badly under the PFIC regime while there is still time to restructure them.