Multi-State Tax Filing for Locum Physicians: What You Owe and Where
Locum tenens physicians who work across multiple states in a single year face a tax filing obligation that most employed physicians never encounter — and that most generic tax guides do not adequately address. Every state where you physically perform clinical work creates a potential state income tax obligation, regardless of where you live, where your entity is formed, or how many days you worked there. Managing that obligation requires understanding how states claim the right to tax you, how they calculate what you owe, and what you can do to minimize the administrative burden without creating compliance risk.
The Core Problem: Every State Wants Its Share
The fundamental principle driving multi-state taxation for locum physicians is source income — income earned from services performed within a state is generally taxable by that state, regardless of where the physician lives. A physician domiciled in Texas — which has no state income tax — who takes a two-week assignment in New York owes New York state income tax on the compensation earned during those two weeks. The Texas domicile provides no protection from New York’s claim on New York-source income.
This principle applies in virtually every state that has an income tax. It means a locum physician who works in six states in a single year may owe income tax in all six — plus potentially in their home state on their worldwide income — and must file a nonresident return in each state where they earned income above that state’s filing threshold.
The administrative burden is real. Multi-state filing for a busy locum physician can involve 5 to 10 or more state returns in a single tax year. This is not unmanageable, but it requires organization, accurate recordkeeping throughout the year, and a CPA who has done this before.
Which States Can Tax You and When
States With No Income Tax
Ten states impose no individual income tax as of 2026, making them effectively tax-free for locum physician income earned there: Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming.
New Hampshire completed the sunset of its Interest and Dividends tax on January 1, 2025, making it a clean no-income-tax state as of 2026. All individual income — including wages and self-employment income — is now untaxed at the state level in New Hampshire.
For multistate locum physicians, these states represent assignment locations where there is no state tax drag on earnings — a meaningful factor when comparing the net value of assignments across different markets.
States That Tax You From the First Dollar
Approximately 22 states impose a filing obligation on nonresidents who earn any amount of income within their borders — there is no de minimis threshold below which you escape the filing requirement. Working a single shift in one of these states creates a technical filing obligation, even if the resulting tax liability is small.
For practical purposes, a very small amount of income in a state may produce a very small tax liability — but the filing obligation still exists. Physicians who work occasional single-day coverage assignments in states with no de minimis threshold should track those income amounts and include them in their annual multi-state filing analysis.
Filing Thresholds vs. Withholding Triggers — A Critical Distinction
Many physicians confuse two separate concepts: the threshold that triggers a filing obligation and the threshold that triggers withholding by the payer. These are different rules that apply independently.
A filing obligation means you are required to file a nonresident return in that state. A withholding trigger means the agency or facility paying you is required to withhold state tax from your payment. You can have a filing obligation without withholding being applied — which means the tax due is your responsibility to pay through estimated payments.
| State | Filing Threshold (Nonresidents) | Withholding Trigger |
|---|---|---|
| California | $1 of income / 1 day | Over $1,500 in payments |
| Illinois | Over 30 days worked | Over 30 days worked |
| Georgia | Over 23 days OR over $5,000 | Over 23 days OR over $5,000 |
| Arizona | $1 of income / 1 day | Over 60 days worked |
For conceptual illustration only. Thresholds change — verify current rules for each state with a qualified tax professional before filing.
How States Calculate What You Owe
The Duty Days Method
The most common method states use to calculate a nonresident physician’s tax liability is the duty days allocation — a proportional calculation based on the number of days worked in the state relative to total working days for the year.
The basic formula: days worked in State X divided by total working days in the year, multiplied by total income for the year, equals the income allocated to State X. That allocated income is then subject to that state’s nonresident tax rate.
A physician who works 260 total days in a year and spends 20 of those days on assignment in Colorado has allocated approximately 7.7% of annual income to Colorado — and owes Colorado income tax on that portion. This method makes precise day tracking essential. Physicians who cannot accurately document how many days they worked in each state face a more difficult tax filing process and potentially less favorable allocations if estimates must be used.
Source Income Method
Some states use a source income approach rather than duty days — taxing the specific compensation paid for services performed within that state rather than a proportional allocation of total income. For locum physicians receiving separate payments from different facilities in different states, this can produce a similar result to the duty days method, but the calculation methodology differs.
Your CPA will apply the correct method for each state — but you need to provide accurate source data about where and when you worked and how much you were paid for each assignment.
Your Home State and the Credit for Taxes Paid
Most states that have an income tax provide a credit to their residents for income taxes paid to other states on income that is also taxed by the home state. This credit prevents true double taxation — you pay the higher of the two states’ rates rather than both states’ rates in full.
How this works in practice: a physician domiciled in a state with a 5% income tax rate who earns income in a state with a 9% rate pays 9% to the work state and receives a credit against the 5% home state tax, resulting in a net rate of 9% on that income. If the home state rate were higher than the work state rate, the physician would pay the difference to their home state after the credit.
For physicians domiciled in no-income-tax states, this dynamic does not apply — there is no home state tax to credit against, and each work state’s tax is simply paid without offset. The credit calculation can become complex when income is earned in many states at different rates — another reason why a CPA experienced in multi-state physician returns is worth the cost.
Withholding in Multi-State Assignments
State withholding requirements for nonresident contractors vary significantly. Some states require agencies or facilities to withhold state income tax on compensation paid to nonresident physicians once they exceed a threshold. Others leave withholding optional or apply it only to W-2 employees rather than 1099 contractors.
The practical implication: do not assume that because no withholding was taken from an assignment payment, no state tax is owed. The absence of withholding does not equal the absence of tax obligation. Physicians who receive 1099 income from assignments in multiple states with no withholding need to make estimated tax payments to those states throughout the year to avoid underpayment penalties.
Reciprocity Agreements — Limited Relevance for Locums
Some pairs of states have reciprocity agreements that allow residents of one state to pay income tax only to their home state on wages earned in the other state — examples include Illinois and Indiana, and Virginia and the District of Columbia. For most locum physicians, these agreements have limited practical impact. They typically apply to W-2 wage earners who regularly commute across a state border, not to 1099 contractors on temporary assignments across many states. Verify whether reciprocity applies to your specific situation with a CPA before relying on it.
The QBI Deduction and Multi-State Income
Locum physicians who qualify for the Section 199A Qualified Business Income deduction should understand how it interacts with multi-state income. The QBI deduction was made permanent and increased to 23% by the One Big Beautiful Bill Act signed in July 2025 — but for physicians, the SSTB classification creates a critical limitation.
Medicine is a Specified Service Trade or Business under Section 199A. This means the QBI deduction phases out as taxable income rises above the threshold — approximately $201,750 for single filers and $403,500 for joint filers in 2026. Most full-time attending physicians earning significant locum income will fall above these thresholds and will be partially or fully phased out of the deduction. The 23% rate applies only to income below the phase-in range.
The multi-state dimension: total income across all states affects where you land relative to the phase-out threshold. A physician working at moderate volume in multiple states may find their combined income pushes them into or through the phase-out range. This is worth modeling with your CPA as part of the annual tax planning conversation.
How Business Structure Affects Multi-State Obligations
Whether you receive locum income as a sole proprietor, through a single-member LLC, or through an S-Corp affects how multi-state income is reported and in some cases whether additional state filings are required for the business entity itself.
Sole proprietors and single-member LLCs report income on Schedule C and file nonresident returns as individuals in each work state. This is the simplest structure from a multi-state perspective.
S-Corp physicians face an additional layer of complexity — state nexus for the entity itself. When your S-Corp performs services in a state, that state may view your entity as doing business there and require the corporation to register as a foreign entity, obtain a Certificate of Authority, and file a state-level corporate return. This applies even if you only worked a single weekend in that state.
For a full breakdown of how the S-Corp election works for locum physicians, see our S-Corp Election guide. For how stipends interact with state tax obligations, see our Housing Stipends and Taxes guide.
Recordkeeping: What You Need to Track All Year
Accurate multi-state tax filing depends entirely on the quality of the records you maintain throughout the year. The minimum recordkeeping for a multi-state locum physician:
- A running log of every assignment — facility name, state, start date, end date, and total days worked
- Separation of income by state — what you were paid for each assignment in each state
- All 1099s and W-2s received, organized by state
- Documentation of travel days — days spent traveling between assignments may or may not count as work days depending on the state and method used
- Records of any state tax withholding applied to assignment payments
- Quarterly estimated tax payment records for each state where you are making payments
The simplest approach is a running spreadsheet maintained in real time — updated after each assignment with the relevant details. A spreadsheet that takes two minutes to update after each assignment takes hours to reconstruct at tax time and may still be incomplete.
Estimated Tax Payments Across Multiple States
Most states that tax nonresident income expect quarterly estimated tax payments when withholding is not covering the liability. For a locum physician working in six states with no withholding, that means potentially six sets of quarterly estimated payments — in addition to federal estimated payments — to avoid underpayment penalties.
Your CPA should help you calculate estimated payment amounts for each state at the start of the year based on projected income and provide payment due dates and account information for each state. The cost of getting this wrong is penalties and interest from multiple states simultaneously — an expensive and avoidable outcome.
Planning Strategies to Manage Multi-State Tax Burden
Multi-state taxation is largely unavoidable for locum physicians who work across state lines — but there are legitimate planning strategies that can reduce the total burden.
Concentrating assignment volume in no-income-tax states is the most direct approach. A physician who can fill 40% of their annual assignment schedule in Texas, Florida, Washington, or other no-income-tax states reduces the total state tax burden on that portion of income to zero. The tradeoff is geographic inflexibility — the best-paying or most convenient assignments may not always be in no-income-tax states.
Tracking days carefully allows you to take advantage of de minimis thresholds where they exist. If a state exempts nonresidents who work fewer than a threshold number of days, staying below that threshold for any given state eliminates the filing obligation for that state — but only if your records support it.
Working with a CPA who specializes in multi-state physician taxation — not just a generalist — is the highest-value planning step available. The difference is measured in hours of their time, in errors caught, and in missed credits and deductions that a specialist would catch automatically.
The Bottom Line
Multi-state tax filing is one of the most administratively complex aspects of a locum career — and one of the most commonly mismanaged. The foundation of a manageable multi-state tax situation is simple: track where you work and for how long, in real time, all year. Everything else — the returns, the estimated payments, the credits — follows from that data. Without it, you are guessing, and in multi-state taxation, guessing is expensive.
The state guides on this site include state-specific tax information for each state covered. For the no-income-tax states and their locum markets, see our guides on Texas, Florida, Alaska, Wyoming, and Washington.
Note: State guide links above use placeholder slugs — verify actual published URLs before this article goes live.