W-2 Box 15 — State · Employer's state ID number

Tax return implications

• Multiple state lines in Box 15 mean you likely have filing obligations in each of those states — check whether each was a withholding-only stop or a genuine tax liability before skipping a return.
• Box 16 (state wages) can differ from Box 1 (federal wages) — states don't all recognize the same pre-tax deductions the federal government does, so don't assume the two figures should match.
• Box 17 (state tax withheld) is the credit amount you carry to your state return's payments line — verify it against your final pay stub's year-to-date state withholding to catch a payroll error before you file.
• If you paid tax to more than one state on the same income, your resident state generally allows a credit for taxes paid to the other state — this is what prevents double taxation, but you have to compute and claim it; it isn't automatic.
• Remote workers should treat Box 15 as reflecting where the employer withheld, not necessarily where they owe tax. New York, for example, treats a nonresident's telecommuting days as New York work days unless the employer has established a bona fide employer office at the telecommuting location, so the employer's state can tax income earned at a kitchen table two states away. A small number of other states apply a similar test — check the employer state's own department of revenue before assuming your home state gets it all.

Common pitfalls & things to check

• If Box 15 shows the wrong state for a remote worker — a common payroll mistake when someone moves mid-year — request a corrected W-2c from your employer rather than trying to reallocate the wages yourself on your return.
• A blank Box 15 doesn't always mean 'no income tax state' — it can also mean the employer simply didn't withhold, which can leave you owing an estimated-tax underpayment penalty in a state that does tax the income.
• Nine states have no individual income tax, so a blank Box 15 is expected for work performed there — but confirm which state actually applies; a remote worker physically in a no-tax state can still owe tax to the employer's state when that state treats telecommuting days as days worked there.
• Don't assume Box 16 (state wages) equals Box 1 — states differ on the tax treatment of certain pre-tax benefits, and a mismatch you didn't expect is often correct, not a W-2 error.
• Credit-for-taxes-paid-to-another-state calculations are done on the resident state's return, not the nonresident return — file the nonresident return first so you know the actual tax paid to plug into the credit worksheet on your resident return.

Related W-2 boxes