Am I a US tax resident if I live outside the country?

Which tests decide whether you are a US tax resident?

Separate the two cases. A US citizen or resident alien who lives abroad is taxed on worldwide income; leaving the country does not remove the filing obligation, and relief comes through exclusions and credits instead. For an individual who is not a US citizen, Publication 519 is the guide: it classifies aliens as non-resident aliens or resident aliens and sets out how to determine which applies.

Two separate tests can make a non-citizen a resident, and meeting either one is enough. The green card test looks at status rather than days: you are a resident for federal tax purposes if you are a lawful permanent resident at any time during the calendar year, which generally means USCIS has issued you a Permanent Resident Card, Form I-551. Residence under that test persists until you renounce and abandon the status in writing, or USCIS terminates it, or a federal court does — living abroad does not by itself end residence under this test.

The substantial presence test is the day-count route. Meeting either test for a calendar year means being considered a United States resident for tax purposes for that year, which changes what has to be reported and can bring foreign account reporting into play at the same time.

How does the substantial presence test count days?

You meet the test if you were physically present in the United States on at least 31 days during the current year and on at least 183 days across the three-year period consisting of the current year and the two years immediately before it. The three-year count is weighted: all the days in the current year, one third of the days in the first prior year, and one sixth of the days in the second prior year.

The weighting is what catches people out. The IRS worked example is someone present on 120 days in each of three consecutive years. The weighted total is 120 plus 40 plus 20, which is 180 days, so the test is not met even though the raw count across three years is far higher. For this test, the United States means the 50 states and the District of Columbia, together with territorial waters and certain adjacent seabed; it does not include US territories or US airspace.

Which days do not count?

You are treated as present on any day you are physically in the country at any time, with specific exceptions. Days you commute to work in the United States from a residence in Canada or Mexico, if you regularly commute, do not count. Neither do days you are in the country for less than 24 hours in transit between two places outside it, days as a crew member of a foreign vessel, or days you were unable to leave because of a medical condition that developed while you were here.

Days as an exempt individual are also excluded, and the term means a visa category rather than someone exempt from tax: certain 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 competing in a charitable sports event. Excluding days on the exempt-individual or medical grounds requires Form 8843, filed with the tax return or sent separately by the return due date. Filing it late generally means the days cannot be excluded, unless you can show by clear and convincing evidence that you took reasonable steps to learn of and comply with the requirement.

What if you meet the test but your life is elsewhere?

Meeting the substantial presence test is not the final word. The closer connection exception can allow someone who met the test to be treated as a non-resident of the United States for tax purposes, and there is a separate version of that exception for foreign students. An income tax treaty between the United States and another country can also change the outcome. Each route has its own conditions and its own disclosure, so the position needs to be documented rather than assumed.

One boundary is worth stating plainly. Tax residence and immigration status are two different systems that borrow each other's vocabulary. Your visa class affects the tax answer, but questions about your immigration standing, or about how a filing position might interact with it, are for an immigration attorney rather than an accountant. A CPA can determine and file the tax position; the lawyer handles the status.