Foreign taxpayers must first determine resident or nonresident status. Nonresidents typically file Form 1040-NR and face 30% withholding on U.S.-source income unless treaties apply. Residents file Form 1040/1040‑SR and report worldwide income. Deadlines vary: April 15 for wage-withheld nonresidents and June 15 for many without wage withholding. Couples may elect resident status; dual-status years require splitting income.
