How does the Substantial Presence Test work?

Apply both numerical requirements

Start with the current calendar year, not a rolling twelve-month period. You need at least 31 countable days in that year before the weighted formula can establish residency. Then add current-year days, one-third of days in the immediately preceding year and one-sixth of days two years earlier. The total must reach 183. Staying under 183 actual days this year does not automatically make you a nonresident, because earlier visits still contribute to the formula.

Identify days that count

Generally, being physically present for any part of a day counts as a U.S. day. Limited exclusions can apply to regular commuters from Canada or Mexico, certain transit of less than 24 hours, certain foreign vessel crew members and days you could not leave because of a medical condition that arose while you were in the United States. Each exclusion has conditions. Do not remove arrival or departure days simply because the visit lasted only a few hours.

Exempt individuals are not automatically tax-exempt

Certain students, teachers, trainees, foreign government-related individuals and qualifying athletes may exclude days as exempt individuals. This term concerns day counting, not a blanket exemption from U.S. income tax. Visa category, prior years in exempt status and compliance with the applicable conditions matter. Form 8843 is generally used for exempt-individual and qualifying medical-condition day exclusions. Some categories have different documentation rules, so the correct filing should be checked rather than assumed.

Meeting the formula is not the final step

A closer connection exception may apply if you have fewer than 183 actual U.S. days in the current year, a foreign tax home throughout that year, stronger foreign connections and no disqualifying permanent-residency steps. Treaty relief may require a different analysis. If no exception applies, determine the residency start date and whether the year is dual-status. Keep separate calculations for income tax residency and other rules that also use day counts; similar numbers do not mean identical tests.

Common mistakes

• Counting all three years at full value.
• Assuming every student can exclude days indefinitely or that a tourist visa prevents tax residency.

Filing requirements

• Keep a dated travel spreadsheet backed by passports, tickets and entry records.
• Check Form 8843 or Form 8840 requirements before claiming excluded days or an exception.

Potential penalties

• An incorrect residency classification can lead to unpaid tax and missing foreign information return penalties.

Related IRS forms

• Form 1040
• Form 1040-NR
• Form 8840
• Form 8843

What to consider next

• Calculate both the current-year minimum and the weighted total.
• Document each excluded day and review the requirements for any exception.
• Have Chirino USA review the calculation before filing as a nonresident.