SITW on your paycheck stands for State Income Tax Withholding. It’s the money your employer takes out of your gross pay each period and sends to your state’s revenue department toward your annual state income tax bill. If you live and work in one of the nine states without a wage income tax, you won’t see this line at all.
Other Names for the Same Deduction
Payroll systems don’t agree on abbreviations. The same withholding might show up as SITW, SIT, ST, State W/H, or plain State Tax. They all mean the same money going to the same place.
A few nearby line items look similar but aren’t the same thing. SDI is State Disability Insurance and SUI is State Unemployment Insurance; those fund different programs and follow their own rules. FITW or FIT is Federal Income Tax Withholding, which goes to the IRS rather than your state.
What Determines the Amount Withheld
Your employer plugs several variables into your state’s withholding formula each pay period. Gross pay is the biggest one. In roughly 26 states and the District of Columbia, rates climb with income under a progressive bracket system. Another 15 states apply a single flat rate to all taxable wages.
Filing status matters too. The state withholding form you filled out at hire tells your employer whether to use the single, married, or head-of-household table. Some states also let you claim allowances or dependents on that form, which reduces the taxable portion of each paycheck before the rate is applied.
Pre-Tax Deductions Shrink the Base
Certain deductions come out of your pay before state tax is calculated, so they lower the wages your SITW is figured on. Common ones include traditional 401(k) or 403(b) contributions, employer-plan health insurance premiums, HSA contributions, and money set aside in a Flexible Spending Account for medical or dependent care.
If you earn $4,000 in a pay period and put $400 into a 401(k), your state withholding is generally calculated on $3,600 rather than the full $4,000. A few states handle specific items differently. Some, for example, don’t treat HSA contributions as pre-tax at the state level, so the effect on your SITW can vary depending on where you live.
States Where You Won’t See SITW
If you live and work in one of these nine states, there’s no state income tax line on your stub:
- Alaska
- Florida
- Nevada
- New Hampshire
- South Dakota
- Tennessee
- Texas
- Washington
- Wyoming
New Hampshire used to tax interest and dividend income, but that tax was fully repealed effective January 1, 2025, so the state is fully income-tax-free for 2026 and beyond.1NH Department of Revenue Administration. Repeal of NH Interest and Dividends Tax Now in Effect Washington doesn’t tax earned wages either, though it imposes a separate 7% tax on long-term capital gains above $270,000; that tax wouldn’t show up as SITW on a typical paycheck.
Living in a no-income-tax state doesn’t erase every deduction. Federal income tax, Social Security, and Medicare still come out of every check, and several of these states lean on higher sales or property taxes to make up the difference.
Why Bonus Checks Look Different
State withholding on a bonus, commission, or other supplemental pay often looks off compared to a regular check. Employers generally use one of two methods.
Under the flat-rate method, the employer withholds a fixed percentage that the state publishes for supplemental wages. Some states set that rate below 3%; others go above 10%. Under the aggregate method, the bonus is added to your regular wages and the whole amount is taxed as if it were a single paycheck, which can temporarily push you into a higher bracket. In states without a published supplemental rate, employers default to the aggregate method or the regular tables.
Either way, the withholding on a bonus isn’t an extra tax. It’s an advance toward your annual state liability, and if too much comes out, you get it back when you file.
Remote and Multi-State Workers
If you work in more than one state, or remotely for an employer based elsewhere, SITW gets more complicated. A state can generally require your employer to withhold its tax if you’re physically working within its borders, even if the company is headquartered somewhere else. Day-count thresholds for nonresident withholding vary, running from as few as 14 days in some states to 60 in others.
A handful of states apply a “convenience of the employer” rule that can catch remote workers. Under it, your wages may be taxed by the state where your assigned office sits, even if you never physically work there, unless your remote setup exists for genuine business necessity rather than personal preference. New York, Delaware, Connecticut, Nebraska, Oregon, and Pennsylvania each enforce some version of this rule.
When an employer withholds for a state you don’t live in, you’ll usually file a nonresident return in that state and claim a credit on your home state return for the tax paid, which keeps the same income from being taxed twice.
Reciprocity Agreements
Neighboring states sometimes have reciprocity agreements that simplify cross-border commuting. Under one of these, your employer withholds only for the state where you live, not the state where you work. Reciprocity pairs exist across dozens of states, especially in the Midwest and Mid-Atlantic.
To use one, you generally file an exemption form with your employer certifying that you’re a resident of the reciprocal state. Skip that step and your employer may default to withholding for the work state, leaving you to sort it out through returns in both states.
Military Spouse Protections
If you’re the spouse of an active-duty servicemember and you live in a state only because of your spouse’s military orders, federal law lets you keep your tax residence in your home state. Your employer can withhold SITW for that home state instead of the state you’re stationed in. You and your servicemember spouse may also elect to use either spouse’s home state or the permanent duty station for tax purposes.2Office of the Law Revision Counsel. 50 USC 4001 Residence for Tax Purposes To claim the exemption, notify your employer and fill out the appropriate withholding form so payroll knows which state should receive the money.
Changing How Much Comes Out
You can adjust your SITW at any time by giving payroll or HR a new state withholding form. Every state with an income tax has its own version, available through your employer or the state tax agency’s website. On it, you update your filing status, allowances or dependents, and any extra dollar amount you want withheld per paycheck. The change generally takes effect within one or two pay cycles.
Good times to submit a new form include marriage, a new child, a second job, or buying a home. Reviewing it once a year is worth doing even in quiet years, because small income or deduction shifts add up.
If Your Withholding Is Off
Withhold too much and you’ll get a refund at tax time. That feels good, but it means the state held your money interest-free all year. Consistent large refunds are a sign to reduce allowances or trim any extra withholding on the state form.
Underwithholding costs more. If your payments fall short of what you owe, you’ll have a balance due at filing, and most states add an underpayment penalty. The federal safe harbor lets you avoid penalties if withholding and estimated payments cover at least 90% of the current year’s tax or 100% of the prior year’s (110% if your adjusted gross income was over $150,000).3Office of the Law Revision Counsel. 26 USC 6654 Failure by Individual to Pay Estimated Income Tax Many states mirror those thresholds, but not all, so check your state agency’s rules.
Realizing mid-year that your withholding is off is usually a form fix: hand payroll a new state withholding certificate. If paycheck withholding alone won’t close the gap, for example when you have freelance income or investment gains that no employer touches, you can send estimated payments directly to the state.4Internal Revenue Service. IRS Publication 505 Tax Withholding and Estimated Tax