Box 16 on your W-2 reports the wages your employer treated as subject to state income tax. That figure flows into your state income tax return as the starting point for calculating what you owe the state, and it often doesn’t match the federal wages shown in Box 1 because states set their own rules about which paycheck deductions reduce taxable pay.
How Boxes 15, 16, and 17 Fit Together
Boxes 15 through 20 on the W-2 are reserved for state and local tax information.1Internal Revenue Service. General Instructions for Forms W-2 and W-3 (2026) – Section: Specific Instructions for Form W-2 Box 15 names the state and gives your employer’s state tax ID number. Box 16 is the wage amount that state considers taxable. Box 17 is the state income tax your employer actually withheld from your paychecks over the year.
Read as a set, Box 16 tells your state what to tax and Box 17 tells it what you’ve already paid in. When you file your state return, you compute your real liability from the Box 16 wages (plus any other income and allowed deductions). The Box 17 withholding is then applied as a credit. Withheld too much, and you get a refund. Withheld too little, and you pay the gap.
Why Box 16 Doesn’t Match Box 1
A difference between Box 1 and Box 16 is normal and usually traces back to one thing: each state decides on its own which pre-tax deductions reduce taxable wages, and those decisions don’t always follow the federal rules.
Retirement contributions are the most common cause. Traditional 401(k) contributions made on a pre-tax basis are excluded from federal wages in Box 1.2Internal Revenue Service. Retirement Plan FAQs Regarding Contributions Most states follow the same approach, but a handful treat those contributions as taxable compensation at the state level. In those states, the money you put into your 401(k) still sits inside the Box 16 total even though it was taken out of Box 1. Contribute $10,000 to a traditional 401(k) in a state that doesn’t recognize the exclusion, and your Box 16 will run roughly $10,000 higher than your Box 1.
Section 125 cafeteria plan deductions behave the same way. These cover items like employer-sponsored health insurance premiums and flexible spending account contributions. Federally they come out before Box 1 is calculated. Most states accept that treatment; the ones that don’t will show a Box 16 figure higher than Box 1 by the amount of those deductions.
The gap can also run the other direction. Some states exempt certain types of income the federal government taxes, which pushes Box 16 below Box 1. Either way, the mismatch reflects how your state treats specific deductions, not an error on the form.
What a Blank Box 16 Means
If Box 16 is empty, the usual explanation is that you work in one of the nine states that don’t impose a personal income tax. With nothing to calculate, your employer leaves Boxes 16 and 17 blank, and you won’t file a state income tax return in that state either.
Moving mid-year can make this confusing. If part of the year was in a state with income tax and part in a no-tax state, you should see a Box 16 line only for the taxing state. The no-tax state won’t appear in Boxes 15 through 17 at all. Entries in Box 14 are a separate matter: employers use Box 14 for informational items like state disability insurance, which can exist even in states without a general income tax.
Working in More Than One State
If you earned wages in more than one state during the year, your W-2 will show multiple rows in the Boxes 15 through 17 area. Each row carries a different state abbreviation, the wages allocated to that state, and the tax withheld for it. A single W-2 can list two states; for more, your employer may issue a second W-2.
Employers allocate your pay across states based on where you physically did the work. Spend 70% of your working days in one state and 30% in another, and roughly that split should appear across the two Box 16 lines. The sum of all your Box 16 amounts won’t necessarily equal Box 1, both because of the federal-versus-state deduction differences described above and because allocation formulas vary from state to state.
Working across state lines generally means filing more than one state return. You file a resident return in the state where you live, which taxes your full income, and a nonresident return in each state where you worked. Nonresident filing thresholds vary widely: some states require a return after a single day of work, while others set a minimum income amount that can be several thousand dollars. To avoid being taxed twice on the same wages, your home state will usually credit you for taxes paid to the work states, capped at what your home state would have charged on that income.
Reciprocal Agreements
About 16 states and the District of Columbia have reciprocal agreements that simplify the cross-border case. If you live in one participating state and work in another, your employer withholds only for your home state. Box 16 shows wages assigned to your resident state, and you skip the nonresident return.
Reciprocity isn’t automatic. You have to file an exemption form with your employer to turn it on. Until the paperwork is in place, your employer defaults to withholding for the work state. If that happens, you file a nonresident return in the work state to recover the withholding and make sure your home state return reports the full income. It’s one of the most common fixable multi-state mistakes.
Remote Work and the Convenience Rule
Remote work has complicated Box 16. Most states source wages to where the work is physically performed, so a home-office worker employed by an out-of-state company is generally taxed only by the home state.
Roughly half a dozen states apply a different standard known as the convenience of the employer test. Under that rule, if your remote setup exists for your convenience rather than a true business necessity, your wages are sourced to the state where your employer’s office is located, even if you never set foot there. Box 16 can show wages allocated to the employer’s state, and you can end up owing tax both there and where you actually live and work.
The business necessity standard is deliberately narrow. Working from home because you prefer it, or because your employer permits it, generally doesn’t qualify. Some home states offer a credit for the tax paid to the employer’s state, but the interaction is complex enough to be worth reviewing with a tax professional before filing.
Local Wages Sit in Boxes 18 Through 20, Not Box 16
Boxes 18, 19, and 20 mirror the state boxes but for local jurisdictions such as cities, counties, or school districts that levy their own income tax. Box 18 is the wages subject to local tax, Box 19 is the local tax withheld, and Box 20 names the specific locality. The Box 18 figure won’t necessarily match Box 16, because local rules on taxable compensation can differ from state rules. Local rates commonly fall in the 1% to 3% range, with a few cities higher. If you see entries here, you may owe a separate local return in addition to your state filing.
If Box 16 Looks Wrong
Your employer must furnish your W-2 by early February for the 2026 tax year.3Internal Revenue Service. General Instructions for Forms W-2 and W-3 (2026)4Internal Revenue Service. About Form W-2c, Corrected Wage and Tax Statements5Social Security Administration. Helpful Hints to Forms W-2c/W-3c Filing Use the corrected numbers on your state return. If you already filed before the W-2c arrived, you’ll file an amended state return to adjust the reported income and recalculate the tax.
If your employer hasn’t corrected the error by the end of February, you can escalate to the IRS at 800-829-1040 or a taxpayer assistance center.6Internal Revenue Service. W-2 – Additional, Incorrect, Lost, Non-Receipt, Omitted The IRS will contact the employer and, if needed, send you Form 4852 to use as a substitute W-2, with your figures estimated from your final pay stub.7Internal Revenue Service. About Form 4852, Substitute for Form W-2, Wage and Tax Statement If a correct W-2 later arrives with different numbers, you’ll amend federally with Form 1040-X and file an amended state return too.