What is the Substantial Presence Test and how does it decide if I'm a U.S. tax resident?

The Substantial Presence Test (SPT) is the day-counting formula the IRS uses to decide whether a non-citizen is a resident for tax purposes. You pass it if you were physically present in the U.S. at least 31 days in the current year AND 183 days under a weighted count: all the days this year, plus ⅓ of last year's days, plus ⅙ of the days two years ago. If you meet that 183-day threshold, the IRS generally treats you as a resident alien and taxes your worldwide income. The green-card test is a separate path to residency. Certain days don't count, including days as an exempt individual on an F or J visa. Track your exact entry and exit dates each year, because a few days can flip your filing status. The immigrant-readiness assessment at wealthserene.com/assessments/immigrant-readiness can help you map out your situation.