What is a dual-status tax year and when does it apply to me?

A dual-status year is a single tax year in which you're a nonresident alien for part of it and a resident alien for the rest, which typically happens in the year you arrive in or permanently leave the U.S. For the resident portion you're taxed on worldwide income; for the nonresident portion only on U.S.-source income. You file one return reflecting both, usually a Form 1040 marked "Dual-Status Return" with a Form 1040NR statement attached (or the reverse in a departure year). Dual-status filers can't use the standard deduction and can't file a joint return, which often makes their tax higher. Because of those limits, arriving immigrants sometimes elect the first-year choice or choose to be treated as residents for the whole year. Keep careful records of your residency start date, since it anchors how each dollar of income is split.