Guide
Leaving a state: the record to build while it is still easy
Updated
Everything on this list is free, takes minutes, and is very hard to do retrospectively. That combination is unusual enough to be worth acting on even where you are confident the move is unambiguous.
Fix the date
Choose the date your domicile changed and attach a document to it: the closing statement on the old home, the first day of the new lease, the day the family actually arrived.
Then use that date everywhere. A return that says one thing, a licence that says another and an employer record that says a third is the pattern that turns a routine year into a reviewed one.
Move the everyday things
Driving licence and vehicle registration. Voter registration. Bank and brokerage addresses. The employer payroll address, which is also what drives withholding to the right state.
Doctors, dentists, vets and schools. These carry more weight than their size suggests, because they are where a family actually lives rather than where its post is delivered.
Deal with the old property
If it is sold, keep the closing statement, and check whether the state operates a payment or withholding on a nonresident sale. New Jersey and New York both do, on their own forms, and the question belongs to the settlement agent well before completion.
If it is kept, decide what it is for. Rented out is a clean answer. Available, furnished and used regularly is the answer that keeps a residency question open.
Count days if any state has a day test
Where the state you left uses a statutory residence test, start counting on day one and record it as you go. Part of a day generally counts as a day.
A contemporaneous log is persuasive. A reconstruction from calendar entries and boarding passes two years later is both painful and considerably less so, and it is what people end up doing.
Ask one question of the new state too
Whether it has a residency test you meet earlier than you expected. Arriving is usually simpler than leaving, and the overlap year is where both states have a view.
Where both states plausibly claim the same period, get advice rather than filing and hoping. That situation is resolved through domicile rules and credits, and it is much cheaper to handle before a return is filed than after two of them disagree.