One Income. Five States. Zero Double Tax.

Multi-state tax planning answers one question before year-end: which state gets to tax each dollar you earn? Once that is settled, everything else — withholding, estimated payments, residency documentation, and the stack of state returns — is execution. Get the sourcing wrong and you either pay two states on the same income or get a notice from a state you ignored.

This is different from finding deductions. A missed deduction costs you its value times your tax rate. A sourcing mistake can cost you an entire second state tax bill, plus penalties, plus the cost of a residency audit. The dollar stakes are usually bigger and the fixes are time-sensitive: most of them only work if they happen during the year, not at filing time.

Here is who the table below describes — if you see yourself in it, the rest of this page is for you.

Wages are generally taxed where the work is performed. Your resident state then taxes the same income but gives a credit for tax paid to the work state. Simple in theory. In practice, three things break it.

First, the classic commuter pattern. A New Jersey resident working in Manhattan files a New York nonresident return (Form IT-203) on the New York wages, then claims a resident credit on the NJ-1040 for the New York tax paid. When payroll is coded correctly and both returns are prepared together, the credit largely offsets the New Jersey tax on those wages. When they are prepared separately — or the W-2 splits the wages incorrectly — the credit comes up short and the difference is pure double tax. We see this constantly on returns prepared elsewhere.

Second, convenience-of-the-employer rules. New York and a small number of other states source wages to the employer's location when you work remotely for your own convenience rather than the employer's necessity. That means a remote worker can owe New York tax on days worked from a home office in another state. Whether your facts support an out-of-state position depends on documentation most employees never think to create — which is the planning opportunity.

Third, payroll coding. Employers default withholding to whatever address is in the HR system. Move states, travel for work, or split time between offices, and the W-2 often allocates wages to the wrong state. Fixing it at filing time is painful; fixing it in payroll mid-year is routine. We do the second one.

Locum tenens work is the most concentrated version of the multi-state problem: 1099 income earned in three, four, or five states per year, no employer withholding anywhere, and quarterly estimates that need to be split by state. Most preparers see one locums return a year. We work with locums physicians nationwide — it is one of the reasons physicians are a flagship vertical at Taxstra, and why White Coat Investor had Bryan on the podcast.

A worked example shows why domicile is the biggest lever on the board:

The engagement for a locums physician typically covers the state-by-state filing map, a quarterly estimate schedule split across states, the domicile strategy (including what evidence to build before changing it), and the S-corp analysis once income justifies it. If your situation includes the tax home rules for travel deductions, we cover that too — it is the same fact-building discipline.

Moving from a high-tax state to a no-tax state can be one of the largest recurring tax moves available to a high earner — which is exactly why the state you are leaving may not take your word for it. High-tax states audit departures, and they win when the move is real on paper but thin on evidence.

The common mistake is treating "183 days" as the whole rule. Day counts matter for statutory residency, but domicile — your permanent home, the place you intend to return to — is a facts-and-circumstances test. States look at where your spouse and kids live, where your home and valuables are, your driver's license, voter registration, doctors, gym, and banking patterns. You can spend fewer than half your days in the old state and still lose, because your life never actually moved.

We build the residency change as a project: a documented break from the old state, a new center of life with evidence behind it, and a day log that matches what auditors request — phone records, tolls, flights, card activity. If you are planning a move, start with our guide to moving states and taxes, then bring us the specifics.

For employees, remote work is a sourcing question. For business owners, it is a nexus question: each state where you have employees, contractors, property, or enough sales can require income tax registration, payroll filings, and sometimes sales tax collection. One remote hire in a new state can quietly create three new filing obligations.

Multi-state businesses also have planning opportunities, not just compliance burdens. Apportionment rules determine how much of your profit each state taxes, and many states offer pass-through entity tax (PTET) elections that work around the federal cap on state tax deductions for owners of S-corps and partnerships. Whether a PTET election helps depends on your states and your numbers — it is a modeling exercise, not a default.

We cover the mechanics in depth in our multi-state nexus guide. The service version is simpler to describe: we inventory where your people, property, and sales are, determine which states have a real claim, register where required, and coordinate it with your overall plan so fixing a state problem doesn't create a federal one. Multi-state planning is one piece of a larger strategy — see how it fits the rest at our tax planning hub.

• Genuine multi-state depth. Locum tenens physician taxation, NY/NJ wage sourcing, residency changes, and remote-worker sourcing are core Taxstra specialties — the work we are known for, not an occasional exception.
• A planning firm, not a once-a-year preparer. Sourcing, withholding, and residency can only be fixed during the year. We run proactive, quantified planning engagements so the moves happen while they still count.
• Nationwide and remote, roughly 1,500 clients. We file in all 50 states every year. Your five-state situation is a normal Tuesday here, and the firm is established — not a solo side practice.
• Physician-community trust. Taxstra is a White Coat Investor platinum sponsor, and Bryan appeared on WCI Podcast #459 — the locums and multi-state physician niche knows us by name.
• CPA + MBA-led, tech-forward. Bryan Martin, CPA, MBA leads the firm. A modern client portal (TaxDome) keeps multi-state document collection and deadlines organized instead of buried in email.

If your income is high enough that state tax is a five-figure line item, multi-state planning usually pairs with broader work — see our high-income tax planning page for what that looks like.