Working in Multiple States: Residency vs. Source Income, and the Credit That Stops Double Taxation

Quick note: This post explains multi-state income tax principles for individual filers. State sourcing rules vary; if you're facing a notice from two states claiming the same income, or if you're unsure which returns to file, talk to an enrolled agent or CPA licensed in the relevant jurisdictions. Wynn Tax Solutions helps taxpayers with federal and state tax controversies, including residency audits and double-taxation disputes.

Why two states might tax the same income

U.S. income tax operates on two parallel tracks: your resident state taxes your worldwide income, while any non-resident state taxes only the income sourced to that state. If you live in New Jersey but commute daily to a Manhattan office, New York will tax the wages you earned there (source income), and New Jersey will tax your entire salary (resident income). On paper, that means the same paycheck is taxed twice—until the resident-state credit steps in.

This overlap is legal. States have sovereign authority to tax income earned within their borders, regardless of where the earner lives. At the same time, your home state claims the right to tax everything you earn everywhere, because you receive the benefit of that state's services, roads, and schools. The result: two valid claims, one pile of money.

Resident-state credit for taxes paid to another state

To prevent economic double taxation, nearly every state that imposes an income tax offers a credit for taxes paid to other states. You file as a resident in your home state and as a non-resident in the state where you earned income. When you complete your resident return, you claim a credit—line by line—for the income tax you paid to the non-resident state on the same income.

The credit is usually limited to the lesser of the tax paid to the other state or the amount your home state would have charged on that income. For example, if you live in North Carolina (top rate 4.75 percent as of 2024) and paid California (top rate 13.3 percent) tax on consulting income, North Carolina will credit only the amount it would have taxed—you're still out-of-pocket for California's higher rate on that slice of income.

Most states require you to attach a copy of the non-resident return, or at least a schedule showing the income taxed elsewhere and the tax paid. Common forms include Schedule S in California, Schedule CR in Massachusetts, or a generic "Credit for Taxes Paid to Another State" worksheet. Keep copies of every return and payment confirmation; residency audits often hinge on proof of where tax was actually remitted.

Reciprocity agreements: when you skip the non-resident return entirely

A handful of state pairs have signed reciprocity agreements that eliminate dual filing altogether. Under reciprocity, you pay tax only to your resident state, even if you work across the border. Your employer withholds for your home state (or you file for a refund if they withheld for the work state), and the work state agrees not to tax that wage income.

Current reciprocity pairings include:

• Pennsylvania and New Jersey: NJ residents working in PA file only in NJ; PA residents working in NJ file only in PA.
• District of Columbia, Maryland, and Virginia: Wages earned by a resident of one jurisdiction while working in another are taxed only by the resident jurisdiction.
• Illinois and Iowa, Kentucky, Michigan, Wisconsin: Illinois has bilateral agreements with each.
• Indiana and Kentucky, Michigan, Ohio, Pennsylvania, Wisconsin: Indiana reciprocates with all five.
• Other pairings: Check your state's Department of Revenue website for the current list; agreements can be terminated on short notice (Michigan and Ohio ended reciprocity for tax years after 2023).

Reciprocity typically applies only to wage and salary income. If you earn self-employment income, rental income, or sell property in the reciprocal state, you may still owe non-resident tax on those sources. You also must affirmatively claim reciprocity—usually by filing an exemption certificate (such as Pennsylvania's REV-419 or New Jersey's NJ-165) with your employer at the start of employment.

What counts as source income in a non-resident state

Non-resident taxation hinges on where the income was earned or derived. Wages are sourced to the state where you physically performed the work. If you spent 60 days in your employer's Texas office and 240 days working remotely from your Colorado home, Texas has no income tax, but if the reverse were Illinois and Colorado, Illinois would tax the portion of your salary allocable to the 60 days worked there.

Other common sourcing rules:

• Self-employment income: Sourced to where services were performed. A consultant who flies to California for a three-day engagement owes California tax on the fees from that project.
• Rental real estate: Always sourced to the state where the property sits.
• Business income (S corporation, partnership): Apportioned by formulas that weight sales, payroll, and property. Many states use single-sales-factor apportionment for non-residents.
• Investment income (interest, dividends, capital gains): Generally not sourced to any state for non-residents; your resident state picks it up. A few states (California, New York) will tax gain on the sale of an interest in a pass-through entity doing business in the state.

Because sourcing is fact-intensive, keep contemporaneous records: travel logs, project invoices, and timesheets. A residency auditor will ask you to prove how many days you worked where.

Domicile vs. residency: where you intend to return matters

States distinguish between domicile and statutory residency. Your domicile is the one place you consider your permanent home—the place you intend to return to whenever you're away. You can have only one domicile at a time. Statutory residency, on the other hand, is a bright-line test: if you spend more than a threshold number of days in a state (typically 183 days in a twelve-month period), that state will tax you as a resident for the entire year, even if your domicile is elsewhere.

For example, New York's statutory residency rule snares many taxpayers who maintain a New York City apartment (a "permanent place of abode") and spend more than 183 days in the state, even if they consider their Connecticut house their true home. California uses domicile principles more than a day count but will presume you remain a California domiciliary unless you can prove you established domicile elsewhere with the intent not to return.

Changing domicile requires more than filing a declaration. States look for objective acts: selling or disposing of your former home, registering to vote, obtaining a driver's license, moving your bank accounts and safe-deposit box, changing your will and estate-planning documents to reference the new state, and spending the majority of your time there. If you keep your old country-club membership, maintain a bedroom for yourself in the old house, and fly back every weekend, an auditor will challenge your claimed domicile change.

Common multi-state pitfalls and how to avoid them

Remote work to a state with income tax: The pandemic normalized remote work, and states noticed. If your employer is headquartered in Massachusetts but you worked all year from your Maine home, Massachusetts generally cannot tax that income—Maine will. But a handful of states (New York, for certain employees; Arkansas, Connecticut, Delaware, Nebraska, and Pennsylvania under specific "convenience of the employer" rules) argue that if you could have worked in the office but chose to work remotely for your own convenience, the wages are still sourced to the employer's state. New York's convenience rule has survived court challenges; if you're a New York-based employer's remote worker living in another state, consult a practitioner before assuming you owe tax only to your home state.

Snowbirds: Retirees who split time between a high-tax northern state and a no-tax state like Florida or Texas must watch the day count and domicile factors. Spending 184 days in New York will make you a statutory resident, triggering tax on your worldwide income (including pensions and Social Security if it's federally taxable). Use a contemporaneous calendar—credit-card statements and E-ZPass records are admissible in audits—and be prepared to show you've abandoned your northern domicile if you claim Florida or Texas residency.

College students: Undergraduate and graduate students generally retain their parents' domicile (or their pre-college domicile) unless they take affirmative steps to establish a new one. Working a summer internship in California won't make you a California resident, but if you stay after graduation, accept a permanent job, sign a lease, and register to vote, California will treat you as a resident going forward. Many states offer a credit or subtraction for scholarships and grants, but taxable stipends and wages are fair game.

Mid-year moves: If you moved from Illinois to Texas in July, you'll file an Illinois part-year resident return (reporting worldwide income for the period you were domiciled there and source income for the remainder) and no Texas return (because Texas has no income tax). Timing the move can matter: closing on a new home December 30 versus January 2 can shift an entire year's tax bill.

Filing mechanics: part-year, non-resident, and the credit

When you have multi-state exposure, expect to file at least two returns. If you were a resident of State A all year and earned some income in State B, you'll file a resident return in A (reporting all income) and a non-resident return in B (reporting only B-source income). On the resident return, claim the credit using the schedule your state provides, entering the income taxed by B and the tax paid to B.

If you moved mid-year, you'll file part-year resident returns in both the old and new states. Each return will have a section allocating income between the resident period and the non-resident period. Be meticulous: the sum of income reported on both returns should equal your federal AGI, and any income double-reported should trigger a corresponding credit.

Some states require you to file even if you had minimal source income. Others have thresholds—for instance, you may not need to file a non-resident return if your wages were under a few thousand dollars and fully withheld. Check each state's instructions; missing a filing can start the statute of limitations running (or not running, if the state argues non-filing is fraudulent).

When the credit doesn't fully eliminate double tax

Three scenarios leave you paying more than a single state's tax:

• Work state has a higher rate than home state: If you live in a low-tax state and work in a high-tax state, your home state will credit only its own tax rate on that income. You keep the excess paid to the work state.
• Local taxes: Some states (Ohio, Maryland, Indiana, Pennsylvania) impose local income taxes on top of state tax. Your resident state typically will not credit local taxes paid elsewhere.
• Different definitions of taxable income: States may treat retirement income, Social Security, or military pay differently. If your resident state exempts pension income but the non-resident state does not, you may owe non-resident tax with no offsetting resident tax to credit against.

In these cases, the credit mechanism works as designed—you're simply bearing the cost of a higher-tax jurisdiction's rules.

Residency audits and burden of proof

High-tax states such as California, New York, Massachusetts, and New Jersey actively audit residency claims, especially when a taxpayer reports a move to a no-tax state like Florida, Nevada, or Washington. The burden of proof is on you to show you abandoned the old domicile and established a new one.

Auditors will request cell-phone location data, credit-card statements, veterinary and medical records, club memberships, and even social-media posts showing where you spent time. If the state determines you remained a resident, it will assess tax on worldwide income for the year(s) in dispute, plus interest and penalties. These assessments can easily reach six figures for high earners.

If you receive a residency audit notice, engage a representative before the first interview. Wynn Tax Solutions works with taxpayers facing multi-state residency disputes and can help organize the documentation and negotiate with state auditors. Do not ignore the notice; states share information, and an adverse determination in one state can trigger a copycat audit in another.

Practical steps to stay compliant

• Track your days: Use a calendar app or spreadsheet to log where you sleep each night. Note travel days—most states assign a travel day to your destination.
• Update withholding: If you work remotely in a different state than your employer's headquarters, ask HR to withhold for your resident state or make quarterly estimated payments.
• File the non-resident return first: Calculate the tax you owe to the non-resident state, pay it, then claim the credit on your resident return. Filing in reverse order can delay your resident refund if the state wants proof of the other state's payment.
• Retain all records for at least four years: Most states can audit back three years, and some (California, New York) have longer reach if they allege fraud or non-filing.
• Formalize a domicile change: If you move, execute a written declaration of domicile, file it with the county clerk in your new state if the option exists, and take every objective step to sever ties with the old state.

Bottom line: Working or living in multiple states triggers overlapping tax claims, but the resident-state credit for taxes paid elsewhere usually prevents true double taxation. Reciprocity agreements simplify compliance for wage earners in a few corridors, while domicile and statutory-residency rules determine which state can tax your worldwide income. Remote work, snowbird arrangements, and mid-year moves add layers of complexity that demand careful day-counting and documentation. If you're caught between two states—or facing a residency audit—consult a licensed practitioner who understands both jurisdictions' rules, and keep every record that shows where you were and where you paid tax.