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 current-year days, one-third of prior-year days and one-sixth of second-prior-year days.
The day-count formula
Count three years, not only the Arizona assignment
The substantial-presence test generally counts all U.S. days in the current year, one-third of days in the preceding year and one-sixth of days in the second preceding year. At least 31 days must occur in the current year and the weighted total must reach 183.
Vacation, training, house-hunting and prior business travel can matter. Reconstruct travel from passports, immigration records, calendars, tickets and expense reports.
Excluded days and exceptions
Visa labels alone do not complete the tax analysis
The IRS excludes certain days, including days for some exempt individuals and qualifying transit or medical circumstances. The tax meaning of exempt individual does not simply mean exempt from tax.
Closer-connection, first-year choice and treaty positions have separate requirements and forms. Taiwan's absence from the IRS treaty list makes it especially important not to import a treaty result from another country.
Why status matters
Residency changes the income and account reporting map
A resident alien generally reports worldwide income for the resident period and may have foreign-account information reporting. A nonresident follows different sourcing and return rules.
The day count does not by itself decide every form or Taiwan consequence. Coordinate a U.S.–Taiwan tax review before selling investments, closing accounts or filing an arrival-year return.
Frequently asked questions
Questions employees ask next
What is the substantial-presence test formula?
Generally, at least 31 current-year U.S. days and 183 weighted days using 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 include the days in the travel record and have a tax professional review exclusions.
Does meeting the test mean I report Taiwan income?
A resident alien generally reports worldwide income for the resident period, but starting dates, exceptions and specialized items require return-level analysis.
Primary sources
What this guide is based on
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