The client sounds simple on the phone. One W-2, the wage statement an employer issues. No business, no rentals, no foreign accounts. Then she mentions the year she actually had. She started in New Jersey, moved to Texas in June, and spent September working from her parents' house in Ohio. Her employer withheld for one state the whole time.
Her "simple" return now needs three state filings, two residency analyses, and an allocation workpaper that did not exist an hour ago. Remote work turned this from a rare fact pattern into a routine one, and the extension pile holds more of these returns every year.
Why one federal return becomes four filings
The federal return is the easy part. The client's income is the client's income, wherever she sat when she earned it.
The states disagree with each other about everything after that. Each state where she lived or worked wants its own return, and each return asks a different version of the same question: how much of this income belongs to us?
The mid-year move creates two part-year resident returns. The state she only worked from wants a nonresident return for the wages she earned inside its borders. Some states tax remote workers under a "convenience of the employer" rule, which sources the wages to the employer's state even when the employee worked elsewhere. New York applies this rule aggressively. A preparer who misses it files a clean-looking return that is wrong.
Every extra state multiplies the work
Adding a second state does not add a second unit of work. It adds several.
New forms. Each state has its own part-year and nonresident forms. New Jersey uses Form NJ-1040NR, its nonresident return. New York uses Form IT-203, its combined nonresident and part-year resident return. The allocation schedules do not resemble each other.
New sourcing rules. States count residency days differently, define "domicile" differently, and source bonuses, equity compensation, and severance differently. A bonus paid in July for work done in the spring can belong to a state the client no longer lives in.
Credit calculations. When two states tax the same dollar, one of them usually allows a credit for taxes paid to the other. The credit is limited, the limitation formula varies by state, and the states disagree about which one must give way. An error in one direction double-taxes the client; an error in the other invites a notice.
Withholding cleanup. The employer withheld for one state. The client owes three. The preparer has to reconcile a year of wrong withholding and explain the balance due to a client who thought she was overpaid.
Tax software will not catch a wrong allocation. It accepts whatever the preparer enters and produces a tidy, internally consistent, incorrect return. Each of these steps is individually manageable. Together, on a return billed as "one W-2," they consume a working day.
The fee never covered the research
Here is the commercial problem underneath the technical one. The fee matched the return she described, not the year she had.
A firm can bill a fair fee for a known quantity of work. Multi-state allocation is not a known quantity until the research is done. The preparer cannot quote the sourcing rule for a state the firm files in twice a year without looking it up. The lookup takes an hour. The fee assumed it would take none. So firms absorb the overrun, push the return into the extension pile, or hand it to the partner — the only person who remembers the convenience rule — and let the firm's most expensive hour carry the loss.
Now change one assumption. Suppose the preparation is priced per return, not per hour. The research cost does not disappear; it moves. A desk that prepares multi-state returns every week is not looking up the convenience rule — it applied that rule on Tuesday. The sourcing questions your firm meets twice a year are questions it answers constantly, and the hours they take sit inside the desk's flat price, not inside your busiest month.
Your side of the transaction becomes fixed and predictable. You know the preparation cost before you commit. You receive a return that two IRS-licensed enrolled agents have already reviewed, with the allocation documented, ready for your own review. Your client, your letterhead, your signature — the firm stays preparer of record and files the return.
The three-state W-2 client stops being a problem to absorb. She becomes a return with a known cost and a known margin.