How is my state tax residency determined when I'm a new immigrant?

State residency is decided separately from federal rules, and most states don't use the Substantial Presence Test at all. Instead they look at domicile—your true, permanent home—and statutory tests such as where you live, work, register your car, and how many days you spend in the state (many use a 183-day rule). You can be a federal nonresident alien yet a state resident if you've settled in a state, which means you may owe state income tax on income the federal form doesn't even count. States like Texas and Florida levy no income tax, so where you land matters financially. New immigrants often file a part-year state return for their arrival year. Check your specific state's rules early, because some states tax worldwide income for residents while others only tax in-state-source income for part-year filers.