The IRS substantial-presence test generally requires at least 31 U.S. days in the current year and 183 weighted days across three years: all of the current year’s days, one-third of the prior year’s and one-sixth of the year before that.
The day-count formula
The count covers three years, not only the Arizona assignment
The substantial-presence test generally counts all of your U.S. days in the current year, one-third of your days in the preceding year and one-sixth of your days in the second preceding year. At least 31 days must fall in the current year, and the weighted total must reach 183.
Vacation, training, house-hunting and prior business travel can all matter. Reconstruct your travel from passports, immigration records, calendars, tickets and expense reports — then give the exceptions their turn.
Minimum U.S. days required in the current year
The weighted three-year total the test must reach
Of the preceding year’s U.S. days count toward the total
Of the second preceding year’s U.S. days count toward the total
IRS substantial presence test
Excluded days and exceptions
Which days can drop out — and which claims need their own forms
The IRS excludes certain days, including days for some exempt individuals and qualifying transit or medical circumstances. One vocabulary trap: the tax meaning of exempt individual does not simply mean exempt from tax.
Closer-connection, first-year choice and treaty positions each have separate requirements and forms — and Taiwan’s absence from the IRS treaty list makes it especially important not to import a treaty result from another country. What rides on all this counting is the scope of your reporting.
Why status matters
Meeting the test redraws your reporting map
As a resident alien you generally report worldwide income for the resident period, and you may have foreign-account information reporting on top. As a nonresident you follow different sourcing and return rules.
The day count does not by itself decide every form or every Taiwan consequence. Coordinate a U.S.–Taiwan tax review before selling investments, closing accounts or filing an arrival-year return — and read this guide as preparation, not as individualized advice, since current plan documents control any TSMC benefits in the picture.
Frequently asked questions
Questions employees ask next
What is the substantial-presence test formula?
Generally: at least 31 current-year U.S. days, plus 183 weighted days counting all current-year days, one-third of prior-year days and one-sixth of second-prior-year days.
Do vacation days in the United States count?
They generally can. IRS exceptions are specific, so put every day in the travel record and have a tax professional review the exclusions.
Does meeting the test mean I report Taiwan income?
As a resident alien you generally report worldwide income for the resident period — but starting dates, exceptions and specialized items still require return-level analysis.
Primary sources
What this guide is based on
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