The form is not optional, and neither are you
A contractor sends an invoice and goes quiet on the one thing you asked for, the tax form. A foreign contractor will not return a Form W-8BEN. A US contractor will not send a W-9. The payment is due, and the easy read is that the missing form is the contractor’s problem, so you pay and move on.
That read is wrong, and it is expensive. A missing form does not put the payment outside the rules. It puts the payment under the IRS presumption rules, which decide the payee’s status for you when you have nothing reliable on file. Once that happens, the obligation to withhold can land on you, and so can the liability if you do not.
This guide walks the verified path with the IRS citations attached: what the presumption rules do, the two withholding outcomes they produce, why the payer carries the liability, and the two practical choices that keep you clean. A quick note first. This is general information, not tax or legal advice. Withholding and reporting outcomes turn on the facts of your situation, so confirm the specifics with a qualified tax professional before you pay.
What a missing form actually triggers
The tax form is your documentation. It tells you whether the payee is foreign or US, and it lets you apply the right treatment with confidence. Take it away and you are not in a neutral state, you are in a documented gap that the IRS has already written rules for.
IRS Publication 515 states the trigger plainly. Per the Publication 515 presumption rules:
“if you have received no documentation or you cannot reliably associate all or a part of a payment with documentation upon which you can rely, then you must apply certain presumption rules”
Read the verb. You must apply them. The presumption rules are not an option you can decline by paying quickly. They are what fills the hole the missing form left, and they decide the payee’s status without the payee’s input.
The two ways the presumption can fall
The presumption rules push the undocumented payment into one of two buckets, and the bucket sets the withholding.
Presumed foreign, US-source income. When the indications point to a foreign payee and the income is US-source, the payment lands in the nonresident regime. The IRS NRA withholding page states that “Most types of U.S. source income received by a foreign person are subject to U.S. tax of 30%,” under the chapter 3 rules in Internal Revenue Code sections 1441 through 1443. A valid W-8BEN is what would have let you claim a treaty rate to reduce that 30 percent. Without the form, you have no treaty claim to stand on, so the statutory rate is the starting point.
Presumed US person, no correct TIN. When the presumption makes the payee a US person and no correct taxpayer identification number was ever furnished, you are in backup withholding. The IRS backup withholding page states the rate directly, that “the payer is required to withhold at the current rate of 24 percent,” and lists the trigger as the case where “you failed to provide a correct taxpayer identification number (TIN) to the payer for reporting on the required information return.” On the timing, the IRS backup withholding B program says “The payer must begin backup withholding on all reportable payments immediately if no TIN is provided to the payer or if the TIN is obviously incorrect.”
Either way, the missing form does not reduce your duty. It removes the documentation that would have let you apply a lower rate or skip withholding.
Decision table
| What you hold | How the payee is treated | Withholding | What fixes it |
|---|---|---|---|
| No W-8BEN, indications point to foreign, US-source income | Presumed foreign | 30 percent NRA withholding under IRC sections 1441 to 1443 | A valid W-8BEN, which may carry a treaty rate |
| No W-9, presumption makes payee a US person, no correct TIN | Presumed US person | 24 percent backup withholding, begun immediately when no TIN is provided | A correct TIN on a Form W-9 |
| A valid W-8BEN or W-9 on file | Documented, treated per the form | Per the form and any treaty claim | Already cured |
Paying the full amount with no form and no withholding does not appear as a row, because it is not a compliant outcome. It is the outcome that creates the liability described next.
Why the liability is yours, not just the contractor’s
The instinct is that a tax shortfall is the contractor’s problem, because it is the contractor’s income. The withholding rules do not work that way. The duty to withhold sits on the payer, and so does the liability for getting it wrong.
IRS Publication 515 is explicit on this. Per Publication 515:
“As a withholding agent, you are personally liable for any tax required to be withheld. This liability is independent of the tax liability of the foreign person to whom the payment is made.”
The same publication adds that if withholding does not happen and the foreign payee does not settle the tax, both the payer and the payee are liable for the tax, plus interest and any applicable penalties. That is the mechanism that turns a missing form from the contractor’s inconvenience into the payer’s exposure. You held the duty to withhold, you did not withhold, and the liability follows the duty.
This is also why “the contractor refused, so it is on them” is not a defense. The contractor’s refusal is exactly the situation the presumption rules cover, and the presumption rules hand the withholding duty to you.
The cure path for a US payee: the B-notice
When the gap is a US payee with a bad or missing TIN, there is a formal cure process, and it is worth knowing so you are not improvising.
The IRS issues you a CP2100 or CP2100A notice after you file an information return with a missing or incorrect TIN. From there, per the IRS backup withholding B program, “The payer must send the First ‘B’ Notice and a Form W-9 to a payee the first time a payee is listed on the CP2100 or CP2100A notice,” and “The payer must send the Second ‘B’ Notice to a payee after the payee is listed on a CP2100 or CP2100A notice a second time within a three-year period.” That is the B-notice sequence. It is the structured way you chase the W-9 and document that you did, and it is how backup withholding gets started and, once a correct TIN arrives, stopped.
For a foreign payee, there is no B-notice equivalent. The cure is simpler in shape, you collect a valid W-8BEN, ideally before you pay, so the presumption never has to run.
The two practical choices
When the form has not arrived and the payment is due, you have two defensible moves. Pick based on the relationship and your tolerance for friction.
Withhold and keep asking. Apply the rate the presumption produces, 30 percent for a presumed foreign payee with US-source income, or 24 percent backup withholding for a presumed US payee with no TIN, and keep requesting the form in writing. If a valid W-8BEN or W-9 shows up later, you can apply the correct treatment going forward and address any over-withheld amount through the proper channel. This keeps you compliant while the documentation catches up.
Pause payment until you hold a valid form. Make a clean tax form a condition of payment. No valid W-8BEN or W-9, no release. This avoids the withholding mechanics entirely, because you never pay into a documentation gap. It is the cleaner position from a compliance view, and it can be written into the contract so it is not a surprise.
What is not on the menu is the third option people reach for, paying the full amount with nothing withheld and no form on file. That is the one path that leaves the personal liability sitting squarely on you.
Get the documentation right before the payment
Almost every version of this problem disappears if the form is collected up front, before the first payment, as a condition of onboarding rather than a chase after the fact. The presumption rules only run when you have nothing reliable on file, so the fix is to never reach that state.
Work through our W-8BEN collection checklist before your next payment. It is free, instant, and walks the collection steps with the IRS citations attached, so you hold a valid form before money moves and the presumption rules never have to decide anything for you.
When a platform handles it for you
A founder paying one contractor can chase a form by email and hold the payment until it arrives. A team paying contractors across several countries is tracking who is documented and who is not, which presumption applies to each gap, which payments need withholding, and which B-notices are in flight, and that is where the manual approach starts to leak.
Omnivoo Contract Management closes that gap for a flat $49 per finalized contract. We collect the right tax form, run the KYC, draft and manage the contract, and pay your contractors in 150+ countries, end to end, so the documentation is in hand before the payment goes out. Transaction fees are passed through at cost, with no FX markup and no subscription.
Want the answer for your specific setup? See how Omnivoo Contract Management handles contractor documentation end to end, or talk to our team.