The payer’s state tax number on Form 1042-S sits in Box 17b and identifies the withholding agent’s account with the state revenue department named in Box 17c. States use it to match the tax withheld from your payment to the correct payer, and you need it when you file a state return to claim credit for the amount already withheld. If the box is blank, it usually means no state tax was withheld, but occasionally the payer left it off by mistake.
Where the Number Sits on the Form
Form 1042-S reports U.S. source income paid to foreign persons and the tax withheld from it.1Internal Revenue Service. About Form 1042-S, Foreign Person’s U.S. Source Income Subject to Withholding The state reporting lives at the bottom of the form in Box 17, split into three sub-fields:2Internal Revenue Service. Form 1042-S – Foreign Person’s U.S. Source Income Subject to Withholding
- Box 17a shows the dollar amount of state income tax withheld.
- Box 17b shows the payer’s state tax identification number.
- Box 17c names the state that received the withheld funds.
Box 17 is separate from Box 15, which reports intermediary or flow-through entity information. Box 15 also has multiple sub-fields, so it is easy to confuse the two, but nothing in Box 15 relates to state tax.2Internal Revenue Service. Form 1042-S – Foreign Person’s U.S. Source Income Subject to Withholding
What the Number Actually Identifies
The number in Box 17b is not the federal Employer Identification Number that appears elsewhere on the form. It is a separate identifier issued by an individual state’s department of revenue. When a payer registers with a state to withhold and remit income taxes, the state assigns this number so that incoming remittances get credited to the right account. It functions as the payer’s account number with that specific state’s tax office.
You use it when you file a return in the state named in Box 17c. The state matches the number to the payer’s account, confirms the withholding was actually deposited, and credits it against your liability. Without the number, the state has no efficient way to verify the credit you are claiming.
Why Box 17b Is Often Blank
A blank Box 17b does not automatically signal an error. Several common situations produce an empty field.
The Source State Has No Income Tax
Eight states impose no individual income tax at all: Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, and Wyoming.3Tax Foundation. State Individual Income Tax Rates and Brackets, 2026 Washington has no tax on wage or investment income, though it does tax certain capital gains. If your income was sourced in one of these places, the payer had no reason to register for a state tax number or to withhold, and Box 17 will be empty across all three sub-fields.
The Income Wasn’t Sourced to a Taxing State
Even in states that levy income tax, the payment has to be sourced there before withholding applies. Passive income such as dividends or interest often traces to the payer’s headquarters location; if that location sits in a non-taxing jurisdiction, nothing gets withheld. The same result follows when the income has no meaningful connection to any particular state.
A Reciprocal Agreement Applies
Roughly 16 states participate in reciprocal tax agreements that let a resident of one state work in another without withholding in the work state. When you file the correct exemption form with your employer, the payer stops withholding for the nonresident state and Box 17 stays blank. If you are covered by a reciprocity agreement and filed the paperwork, that empty box is the expected outcome.
Nothing Was Withheld
Check Box 17a first. If the withholding figure there is zero or blank, the payer had nothing to report to any state, so there was no reason to include a state tax number. Zero withholding can result from a state-level treaty provision, income below a withholding threshold, or an exemption tied to the type of payment.
What to Do When the Number Is Missing But Shouldn’t Be
If Box 17a shows a real dollar amount and Box 17c names a state but Box 17b is empty, the payer probably made a reporting error. You cannot cleanly claim the state withholding credit without that number, so it is worth fixing.
Confirm the Gap
Verify that 17a contains a positive amount and 17c names a state. Also check whether the same payer sent you more than one Form 1042-S covering different income types, because the state information may appear on one form and not another.
Ask the Payer for a Correction
Contact the withholding agent’s tax or payroll department. Have your taxpayer identification number, the form’s unique identifier, and the tax year on hand. Put the request in writing so you have a paper trail.
When the payer issues a corrected form, they check the “Amended” box at the top, assign an amendment number starting at 1 for the first correction, and keep the same unique form identifier as the original.4Internal Revenue Service. Instructions for Form 1042-S (2026) They must also send the amended version to the IRS, not just to you. Corrections typically take several weeks to arrive.
If your state filing deadline comes first, you can generally file using the withholding amount from Box 17a and the state name from 17c, then amend once you have the complete form. Ask the relevant state revenue department how it wants provisional filings handled.
Deadlines and the Payer’s Exposure
Payers must file Form 1042-S with the IRS and give copies to recipients by March 15 of the year after the income was paid. If that date falls on a weekend or legal holiday, the deadline moves to the next business day.4Internal Revenue Service. Instructions for Form 1042-S (2026) For income paid during 2025, the deadline is March 16, 2026, because March 15 is a Sunday. If you have not received your form by late March, contact the withholding agent; a missing form does not extend your own state filing deadline.
Payers who file incorrect Forms 1042-S face federal penalties of $250 per form, up to $3,000,000 per calendar year, and the penalty drops sharply if they correct the error quickly.5Office of the Law Revision Counsel. 26 U.S. Code 6721 – Failure to File Correct Information Returns Intentional disregard raises the per-form penalty to $500 or 10 percent of the amount that should have been reported, whichever is greater, with no annual cap. States impose their own separate penalties. On a large filing run, a missing state tax number across thousands of forms adds up, which is why most withholding agents respond quickly once you flag the omission.