W-2 Box 15 — State · Employer's state ID number
The state abbreviation and your employer's state tax identification number. Required for every state in which state income tax was withheld.
At a glance — Box 15
- Box name
- State · Employer's state ID number
- Reports to
- Reported on the corresponding state return — not on Form 1040.
- Check against
- Your state's Department of Revenue ID for your employer (usually on their website).
What Box 15 means
Box 15 identifies the state in which your employer withheld state income tax, along with the employer's state ID number (a state-assigned equivalent of the federal EIN). If you worked in multiple states, your W-2 may have multiple Box 15 / 16 / 17 stacks — one per state.
States with no income tax (TX, FL, NV, SD, TN, WA, WY, AK, NH) generally leave Box 15 blank for residents, since no withholding is required. NH taxes interest and dividends only (phased out in 2027); TN historically taxed interest and dividends (Hall Tax, repealed 2021).
Tax return implications
- Drives which state return you must file — if Box 15 shows more than one state, you likely owe state returns in each.
- Multi-state W-2s require coordination of resident and nonresident returns to avoid double taxation (usually via a credit on the resident state's return).
- Remote workers: Box 15 reflects where your employer withheld; your actual state tax residency may differ (particularly relevant for 'convenience rule' states like NY, DE, NE, PA, AR).
Common pitfalls & things to check
- If your W-2 shows wrong Box 15 state (common for remote workers), request a corrected W-2c from your employer — don't try to work around it on your return.
- Living in one state and working in another: you generally file a non-resident return in the work state, then a resident return in the home state claiming credit for taxes paid to the other state.
- Nine states have NO individual income tax — Box 15 may be blank for them even though you worked there.
Related W-2 boxes
Box 1 — Wages, tips, other compensation
Your taxable federal wages for the year — gross pay minus pre-tax deductions like traditional 401(k), Section 125 cafeteria plan contributions, and pre-tax HSA.
Box 2 — Federal income tax withheld
Total federal income tax your employer withheld from your paychecks during the year, based on your Form W-4 elections.
Box 3 — Social security wages
Your wages subject to Social Security tax, capped at the annual wage base. Differs from Box 1 because traditional 401(k) deferrals are not excluded.
Box 4 — Social security tax withheld
The Social Security tax your employer withheld — exactly 6.2% of Box 3 (plus Box 7 tips), capped at 6.2% of the annual wage base.
Reconciling your W-2 at tax time? Use the paycheck calculator to verify expected federal, Social Security, and Medicare withholdings on your salary, and the federal income tax calculator to estimate your refund or balance owing before you file.
Related Calculators
Paycheck Calculator
Federal, state, FICA withholding, net take-home, W-4 alignment
Federal Income Tax Calculator
10–37% brackets, $15,750 standard deduction, progressive calculation
W-4 Withholding Optimizer
Form W-4 allowances, correct federal withholding, avoid penalties
FICA & Social Security
6.2% SS to $176,100, 1.45% Medicare, 0.9% additional Medicare
Tax Refund Estimator
Estimate federal refund, withholding vs liability, adjustments
401(k) Calculator
Contribution limits, employer match, tax-deferred growth
Sources
W-2 box definitions per IRS General Instructions for Forms W-2 and W-3 and IRC §6051. Rates and thresholds current for tax year 2025 (file by April 15, 2026); 2026 figures included where published.