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Short answer
A W-9 vendor request is the step in which a buyer that must file an information return with the IRS asks a U.S. supplier to complete IRS Form W-9, so the buyer has the supplier’s correct name and taxpayer identification number (TIN). The buyer is the “requester”; the supplier provides the form. This page covers the buyer-side intake: what to check on the returned form and what happens if it is missing. It is general information, not tax advice; consult a tax adviser for your own situation.
Definition and scope
The IRS says to use Form W-9 to provide a correct TIN, and its requester instructions say to use it to request the TIN of a U.S. person. A requester is anyone required to file an information return. The form is not a quality or licensing document: it says nothing about whether a supplier’s products are safe, registered or fit for a lab or clinic. Those checks sit in the pages on vendor onboarding documentation and vendor selection criteria.
This guide does not repeat what a supplier setup form contains field by field; see the vendor information form and vendor application form guides for that. It is narrower: the W-9 request as an accounts payable task.
How the W-9 request works in a medical supply purchase
When a lab or clinic adds a new supplier of consumables or equipment, accounts payable (or the purchasing office acting for it) sends the form or collects the same data through its own supplier-setup process. The IRS instructions allow a substitute W-9 built into other business forms if its content is substantially similar to the official form and it carries the required certifications. The IRS lists cases where a signed W-9 may be needed, for example when a withholding agent makes a reportable payment subject to withholding.
When to ask is a process choice. Many organizations collect the form before the first payment so that payment is not held up later; that timing is an accounts payable practice, not a rule stated in the IRS Form W-9 pages cited below.
W-9 intake checklist
| Check on the returned form | What the IRS instructions say |
|---|---|
| Name on line 1 | For a disregarded entity, the owner’s name is reported on line 1. |
| Federal tax classification, line 3a | A non-disregarded LLC has a single box to check on line 3a; for a disregarded entity the box checked is the owner’s classification. |
| TIN in Part I | Part I should carry the supplier’s TIN (SSN, EIN or other TIN). A form with the TIN missing or obviously wrong is not a complete form, and the requester may need to seek a corrected one. |
| Exempt payee code | The instructions say certain payees are exempt from backup withholding; such a payee may enter an exempt payee code on the form. Payments not subject to information reporting are also not subject to backup withholding. |
| Certification, signature and date | A valid W-9 contains the payee’s name and TIN and is signed and dated under penalties of perjury by the payee or an authorized signer. Part II includes the certification relating to FATCA reporting. |
| Electronic collection | The system must reproduce the information on the paper form and must require, as the final entry, an electronic signature by the payee whose name is on the form. |
The rows above come from the IRS instructions. Checking the address against the supplier record and the name against the purchase order are the buyer’s own consistency checks, not IRS requirements. Follow your institution’s rule on how a form containing a TIN may be transmitted and stored; the IRS pages cited below do not set a retention period.
Documents and terms that go with it
A W-9 is one document among several in supplier setup. It answers a tax question only. A health care buyer often pairs it with an exclusion check (see OIG exclusion list checks for medical supply vendors and debarment and exclusion screening) and with the broader vendor due diligence steps. For a related reporting topic, see what a 1099 contractor is.
Missing or incorrect W-9: backup withholding
The IRS says backup withholding can apply when a payee fails to provide a correct TIN when required. The payer withholds at a flat 24% of reportable payments in the listed situations, and the requester instructions say it continues until the cause is remedied. IRS Topic 307 states that a payee stops it by giving the payer a correct name and TIN and certifying that the TIN is correct; after a second notice from the same payer, the payee must provide verification of the correct name and TIN. Topic 307 also says that the IRS notifies the payer when the TIN a payee gave is incorrect, and the payer then notifies the payee. What this means for a given payment is a question for a tax adviser.
Common misunderstandings
- “A W-9 shows the supplier is approved.” It does not; it records name, TIN and certifications. Approval rests on other checks.
- “Any form with a TIN will do.” A valid W-9 must be signed and dated under penalties of perjury, and a substitute must carry the required certifications.
- “A blank or placeholder TIN is a pass.” A W-9 without a TIN in Part I is incomplete; a missing TIN is a reason to ask for a corrected form, not to file it as done.
Frequently asked questions
What is a W-9 vendor?
It usually means a supplier that has been asked to return IRS Form W-9 to the buyer paying it, so the buyer holds the supplier’s name and TIN. The form is the IRS’s tool for obtaining a payee’s correct TIN.
How does a W-9 vendor request work in a medical supply purchase?
Accounts payable or purchasing sends the form (or a substitute carrying the same certifications) during supplier setup, checks the returned form against the checklist above, and holds it with the vendor record under the institution’s rules.
Which documents or terms go with a W-9?
Exclusion screening, vendor due diligence and the supplier information form usually travel with it; terms to know are requester, TIN, exempt payee code and backup withholding.
What mistakes do small buyers make with a W-9?
Accepting an unsigned or undated form, filing a form with no TIN as complete, and assuming the form says anything about product quality. The IRS instructions describe the signature and certification rules above.
Sources
- IRS, About Form W-9 (form revision 0324), checked 2026-11-03.
- IRS, Instructions for the Requester of Form W-9 (revised 03/2024), checked 2026-11-03.
- IRS, Topic no. 307, Backup withholding, checked 2026-11-03.
General information, not tax or legal advice.
