Moving to Another State Mid-Year: How Part-Year Residency Affects Your Income Taxes

Marisol accepted a new job last spring and moved from a rented apartment in Albany, New York, to a house she bought in another state, starting the new role on July 1. Her old employer paid her for the first half of the year, her new one for the second half, and she sold some stock in September. When tax season arrives, she will need to file in two states, and both will want to know exactly when she stopped being a New Yorker.

Her situation is common, and the rules behind it are less intuitive than many people expect. Changing your address does not by itself change where you owe tax, and the date that matters is not always the date of the moving truck. This article explains the core concepts using New York and California as examples. It is general information, not tax advice, and the details vary by state.

Domicile and residency are not the same thing

The first surprise for many movers is that states use two related but different ideas.

Domicile is your permanent home, the place you intend to return to and remain. New York's Department of Taxation and Finance describes it as your permanent and primary residence that you intend to return to or remain in after being away. You can own or rent several homes, but you can have only one domicile at a time.

Residency for tax purposes can be broader. A state may treat you as a resident because you are domiciled there, or because you meet a separate test based on keeping a home there and spending enough time there. That second path is often called statutory residency.

The distinction matters because a move is really a change of domicile. Until the old state accepts that your domicile has changed, it may still treat you as a full resident and tax all of your income.

How a state decides your domicile changed

New York says your domicile does not change until you can demonstrate with clear and convincing evidence that you abandoned your New York domicile and established a new one elsewhere. Its guidance describes this as shifting the focus of your life to the new location, and it notes that filing a certificate of domicile or registering to vote in the new place is not enough on its own.

In practice, states look at the whole picture. Where is your main home, and what happened to the old one? Where do you work? Where are your family, your doctors, your important possessions, and the activities that fill your time? Where are you registered to vote, licensed to drive, and registering your car?

For Marisol, selling or ending the lease on the Albany apartment, moving her belongings, changing her driver's license and voter registration, and starting work in the new state all point the same direction. Someone who keeps the old home, leaves most of their life in place, and spends weekends back in the old state presents a much murkier case.

The day-count rule, and why the number matters

Statutory residency is where day counts come in. Many people have heard that 183 days is the magic number, and some states use a threshold near that. But each state writes its own rule, and the exact number matters.

New York's rule, as described by its tax department, treats you as a resident even if your domicile is elsewhere when you maintain a permanent place of abode in New York for substantially all of the taxable year and you spend 184 days or more in the state during that year. The department adds that any part of a day counts as a day, and that you do not need to be at the home for the day to count.

Both conditions must be met. Someone who spends 200 days in New York but has no permanent place to live there is not a statutory resident under this test, though they may still owe tax on income earned there. Someone who keeps an apartment year round but spends only 150 days in the state is also not a statutory resident under this test. The combination is what triggers it.

This rule mostly affects people who keep a home in New York after moving, or who live elsewhere but keep a pied-a-terre in the state. For a clean mid-year move with no home left behind, it usually does not apply, but anyone keeping property in their old state should track days carefully.

California takes a different approach. The Franchise Tax Board says you are a resident if you are present in California for other than a temporary or transitory purpose, or if you are domiciled in California but outside the state for a temporary or transitory purpose. FTB Publication 1031 lays out the factors it weighs. Rather than a single day count, California looks at the purpose and nature of your time in or away from the state.

What part-year residency means for your income

Once the move date is set, most states split the year in two. For the period you were a resident, the state generally taxes all of your income, wherever it was earned. For the period after you left, it generally taxes only income from sources within that state, such as wages for work physically performed there or rent from property located there.

New York's guidance puts it this way: if you were a resident for only part of the year, your income is split, with part taxed under resident rules and the remainder under nonresident rules. The new state typically does the mirror image, taxing everything you earned after you became a resident and, as a nonresident, any income from its sources before that.

Using Marisol as an example, her wages from January through June would be taxed by New York as resident income. Her wages from the new job after July 1 would generally not be New York income, unless she performed work in New York. The September stock sale happened after the move, so it would usually be taxed by her new state of residence rather than New York, though rules for certain types of income, such as deferred compensation or a business interest, can be more complex.

The forms: New York IT-203 and California 540NR

Part-year residents usually file a special return rather than the standard resident form.

In New York, that is Form IT-203, the Nonresident and Part-Year Resident Income Tax Return. The tax department explains the method: you first calculate your tax as if you were a full-year resident, then determine how much to allocate to New York using an income percentage based on your New York source income compared with your federal income.

In California, the equivalent is Form 540NR. The 2025 instructions tell filers to use Form 540NR if either spouse or registered domestic partner was a nonresident or part-year resident during the year. The return works out the tax on total taxable income, converts that into an effective California tax rate, and applies that rate to the income taxable by California.

Both approaches share a design feature: the state's tax rate is driven by your total income, even though the state taxes only its share. Someone with a large income from the out-of-state half of the year may find that the in-state portion is taxed at a higher rate than they expected.

Avoiding double taxation

When two states could claim the same income, a credit usually prevents the full amount from being taxed twice. New York's guidance says a person who lives in one state but works in another typically receives a credit in their state of residence to eliminate double taxation, and it offers a resident credit for income sourced to and taxed by another state while you were a New York resident.

The credit generally goes to the state of residence and covers the overlap, but only up to limits set by each state's formula. It does not always cancel everything, particularly if the two states' rates differ. Review the credit form for your state of residence, such as New York's Form IT-112-R, when income overlaps.

Remote work after a move

Moving does not always end ties to the old state's tax system if you keep working for the same employer remotely. New York, for example, says that if you are a nonresident whose primary office is in New York, your days telecommuting from outside the state are generally considered days worked in New York unless your employer has established a bona fide employer office at your telecommuting location.

That rule can surprise people who move away but keep a New York job. Their wages may continue to be New York source income. Other states have their own approaches, so anyone working remotely across state lines should look at the rules of both the employer's state and their home state.

Records that support your move date

Because the move date drives so much of the calculation, documentation matters. Useful records include closing or lease documents for both the old and new homes, moving company invoices, the dates on a new driver's license and voter registration, utility start and stop dates, and an employer letter confirming your new work location and start date.

For anyone keeping a home in the old state, a day-by-day log is valuable. Phone location history, credit card statements, and travel records can help reconstruct where you were if a state questions your residency later. New York, for instance, publishes nonresident audit guidelines, a sign that these questions do get examined.

Payroll and estimated payments

Withholding often lags behind a move. If your employer keeps withholding for the old state after you leave, or your new employer has not yet set up withholding for the new state, you may end up with a refund from one state and a bill from the other. Updating your withholding forms promptly with each employer helps keep both closer to accurate.

If you had a large one-time gain, such as Marisol's stock sale, consider whether estimated tax payments to your new state are needed to avoid underpayment charges. Each state sets its own estimated tax rules.

A short checklist for the year of a move

Decide and document the date your domicile changed. Cut ties to the old state where practical, including the home, licenses, and registrations. Track days in the old state if you keep any property there. Allocate each item of income to the right period and state. File the part-year return in each state, such as IT-203 for New York or 540NR for California. Claim any credit for income taxed by both. And update withholding with every employer.

A mid-year move turns one tax return into two, and the date you pick has to hold up under scrutiny. Clear records and a deliberate break with the old state make that date much easier to defend.