Domicile

Your domicile usually decides which state taxes you as a resident. A resident is taxed on all income, including income earned in other states. New York treats anyone domiciled there as a resident, apart from two narrow exceptions for people who spend little time in the state. California keeps taxing people domiciled there as residents while they are away for a temporary or transitory purpose. You can have only one domicile at a time, and you keep it until you acquire a new one. Married couples usually share one domicile, but spouses who are separated in fact may each have their own.

A domicile changes when you move somewhere new, intending to stay there indefinitely. An absence of any length leaves it in place while you still mean to return. Whoever claims the change has to prove it. In New York, your own statements count, but not if the way you live contradicts them.

Domicile and residence are separate tests, and they can point to different states. California’s regulation says you can be a resident without being domiciled there, and domiciled there without being a resident. New York’s statutory resident test ignores domicile altogether. It looks at whether you keep a home in the state and spend more than 183 days there. Domicile itself has no day count.