Start with a one-page timeline
Write the date you moved out of the old home and into the new one. Add the start and end dates of each job, and the state and city where each job's work was done. Note any weeks you worked from home or traveled.
Keep this page with your tax papers. It answers most of the questions a form will ask, and it is the first thing a preparer or an agency letter will ask for.
Proof of the move date
Hold on to the signed lease or closing papers, a utility start date, the moving company invoice or a change of address confirmation. You do not need to send these with a return, but if a state asks, a clear paper trail ends the question quickly.
Voter registration, a driver's license address and the address on bank statements should match the new home over time. Differences are what attract questions.
Gather the income documents
Collect every W-2, 1099 and statement from banks and brokers. Check boxes 15 through 20 on each W-2 for the state, state wages, state tax withheld, and any city tax. Add any unemployment or retirement forms, since those also show state information.
If you expect a form that has not arrived, check the employer's payroll portal. Some employers post W-2s earlier than they mail them.
Ask your employer or payroll
If your address changed, find out whether payroll updated your state and city withholding, and from what date. Ask for a year-end pay stub that shows year-to-date withholding for each place.
Do not ask payroll for tax advice. Ask them to confirm what was withheld and where, and keep their answer in writing.
Match the forms to the places
Make a short list of what you expect to file: federal, the state you left, the state you moved to and, if the city was part of your year, the city piece. Check each year's official instructions for the forms and for how part-year dates are counted.
Tax software that asks where you lived and when can build this list for you. MCC Tax 1040 does this for supported years. Verify the result against the instructions.
Questions to settle before you file
Decide whether any income needs special handling, such as a bonus paid after the move, stock compensation, a side business or rental income. Each can be sourced to a different state than your wages, and each is easier to fix before the return than after a notice.
Confirm your filing status and dependents for the whole year. Those items follow you across the state line, and a mismatch between the federal and state returns is an easy way to trigger a letter. If a spouse lived somewhere else for part of the year, write that down too.
Keep it after you file
Save the return, the timeline and the proof of the move date together. If an agency writes later about residency, you will have the answer in one folder rather than scattered across emails.
Common questions
How long should I keep these records?
Keep tax returns and the records behind them for at least as long as the filing deadline for amending or auditing that year, and longer if you are unsure. Ask a tax professional for your own situation.
What if I cannot find my move date proof?
Use whatever shows when you began living there, such as a lease, a utility start or a bank statement address change, and keep a note of how you chose the date.
Should I use a preparer or software?
Either can work. A mid-year move with multiple states is more complex than a standard return, so decide based on how many income sources and states you have.
This guide is general information, not tax, legal or accounting advice. Rules, fees and due dates change; check with the IRS, the NJ Division of Taxation or a licensed professional for your situation.