What is Substantial Presence Test?

How it works

The IRS uses a single weighted formula. You meet the SPT and become a US tax resident for the year if both of the following are true:

• You were physically present in the US at least 31 days in the current year, and
• The weighted three-year total — current year + 1/3 of last year + 1/6 of two years ago — is 183 days or more.

Any part of a day in the US counts as a full day. Border crossings, layovers without leaving the airport, partial days arriving or departing — all one day each. The formula compounds: 122 days in three consecutive years (122 + 41 + 20 = 183) tips you into resident status, even though no single year hit the headline number.

Once you cross the threshold, the IRS taxes your worldwide income from the first day of your continuous presence that year — Form 1040, including foreign salary, capital gains, partnership distributions, plus FBAR for foreign accounts over $10,000 and FATCA reporting on Form 8938.

Who is exempt

Not every day counts. Days of presence are excluded for individuals in specific statutory categories: F-1 / J-1 / M-1 / Q-1 students for up to five calendar years; J-1 / Q-1 teachers and trainees for up to two; foreign-government and international-organisation employees on A or G visas; foreign-vessel crew between US ports; Canadian and Mexican residents who commute daily to work in the US; and individuals who could not leave because of a medical condition that arose during their stay. Form 8843 is filed each year days are excluded under one of these.

Examples

• The classic snowbird. A Brazilian retiree spends 130 days in Florida in 2026, 130 in 2025, 130 in 2024. The math: 130 + (130/3) + (130/6) = 130 + 43.3 + 21.7 = 195. Over 183, more than 31 in 2026 → US resident for 2026, taxed on worldwide income. Only filing Form 8840 under the closer connection test keeps him out.
• The remote founder. A French SaaS founder visits clients 70 days in 2026, 60 in 2025, 0 in 2024. Total: 70 + 20 + 0 = 90. Below 183 — non-resident. He files Form 1040-NR if he had US-source income, but his French tax base stays untouched by the IRS.

Common mistakes

• Counting only "full" days. Any partial day is a full day. A 4 PM landing at JFK on Monday plus a 7 AM departure Tuesday is two days, not one.
• Ignoring the three-year look-back. People plan the current year and forget the prior two years' weights. 121 days every year for three years gets you to 121 + 40 + 20 = 181 — just under — but a single extra week of travel tips it.
• Assuming a treaty protects you automatically. If a tax treaty applies, you usually still need to file Form 8833 to claim treaty residency override. Skipping that filing means the IRS taxes you as a resident regardless of treaty position.
• Confusing SPT with green card status. Green card holders are residents from day one — the SPT is irrelevant for them. Surrendering a green card without proper documentation can also trigger the exit tax under §877A.