It depends. For your first year in the US, you may be a resident, nonresident, or “dual status” resident (part-year resident and part-year nonresident), depending on your number of days in the US and other factors. Also, in the first year, you can claim special elections or tax treaty benefits to change your residency status or start date. Often, it’s important to work with a tax advisor who can guide you through your options and help you file the best status for your situation.