W-9 collection and vendor onboarding: what legal needs to enforce

Why the W-9 exists

The W-9 is the IRS form a US person gives to a payer so the payer knows who they are paying and how to report it. The vendor fills in their legal name, their tax classification (individual, sole proprietor, C corporation, S corporation, partnership, LLC), their taxpayer identification number, and signs a certification under penalty of perjury. You keep it in your files. You do not send it to the IRS. The information on it drives everything you file at year end: the 1099-NEC you issue to a contractor, the 1099-MISC for rent and other payments, and the backup withholding you may have to apply.

The form is not optional paperwork. The IRS treats the payer as responsible for collecting it. If you cannot produce a W-9 for a vendor you paid reportable amounts to, the IRS presumes the worst and can impose penalties. For a company with dozens of vendors, the W-9 file is the single most checked document in an IRS examination of your information return reporting. See the W-9 collection page for how LawDep tracks this obligation.

The W-8 forms for foreign vendors

A vendor that is not a US person cannot give you a W-9. Instead they give you one of the W-8 series. A foreign individual who receives US-source income provides a W-8BEN. A foreign entity provides a W-8BEN-E, which is a much longer form because the IRS wants to know whether the entity can claim treaty benefits. The W-8 forms are not just for withholding documentation. They also determine whether you are required to withhold 30% on payments to that vendor. If a foreign vendor's W-8BEN-E expires (they are generally valid for three years) and you keep paying them, you become liable for the 30% you failed to withhold. That is the most expensive way to learn the W-8 renewal rule.

Backup withholding: the cost of a missing form

If a vendor refuses to provide a W-9, or provides one that fails validation, the law requires you to withhold 24% backup withholding from their payments and remit it to the IRS. The rule is blunt: no valid TIN, no exception. A contractor who will not give you a W-9 must have 24% of every payment withheld until they do. This is a real cash consequence for your vendor and a real accounting burden for you, which is why legal and finance teams are best off making the W-9 a condition of signing the vendor agreement rather than a chase after the fact.

Validation and TIN matching

The name and TIN on the W-9 should be checked against the IRS TIN matching service before you rely on them. A mismatch means the name does not line up with the number, and the IRS will flag it when you file. The most common cause is a vendor giving you a DBA or trade name instead of the legal name on their tax return, or an LLC giving you its EIN when the IRS expects the owner's SSN because the LLC is a disregarded entity. Getting the classification right on the form fixes most of these.

Making collection part of onboarding

The W-9 is collected once and stays valid as long as the vendor's circumstances do not change. A vendor that changes its legal name, its tax classification, or its address should issue an updated W-9. The practical system is to make the W-9 a required field in the vendor record before the first payment can be approved, and to store the classification and TIN alongside the vendor's contract so year-end reporting does not require reopening every file.

LawDep's vendor workflow treats the W-9 as a document on the vendor record with its own status: collected, validated, or outstanding. The obligation is tracked as a filing on the compliance calendar, so an onboarding that does not include the W-9 shows up as an open item instead of a surprise at year end. When the vendor agreement is signed, the W-9 requirement is already attached to it.

What the legal team should actually enforce

Your vendor agreement should make the provision of a current, valid W-9 a condition precedent to payment. It should also state that the vendor must notify you of any change in its tax classification within a set number of days. The 1099-NEC threshold, currently $600 for most payments, is the number that decides whether a vendor is reportable at all, but the W-9 is collected from every vendor regardless of whether you will issue a form at year end, because the backup withholding rules do not have a threshold.

Put the cycle on a calendar

The W-9 is an event filing: it is due before first payment, and the W-8 renewals are due every three years. Both fit a compliance calendar that watches vendor records. LawDep tracks the initial collection, the W-8 expiry, and the annual 1099-NEC on one rolling schedule so the vendor file stays current without anyone keeping a spreadsheet. Generate a free calendar and map out your vendor compliance cycle.

The 1099-NEC connection

The W-9 file is what makes year-end reporting possible. At the end of the year, every vendor who received $600 or more in reportable payments must receive a Form 1099-NEC, and the amounts on that form must match the classification on the W-9. A contractor paid through a separate legal entity gets the form issued to the entity's name and EIN, not to the individual's SSN, and getting that wrong creates a mismatch the IRS flags. The 1099-NEC deadline is January 31, both for issuing the form to the vendor and for filing the copy with the IRS. See the 1099 filing page for the details.

The two deadlines are tight: the vendor file must be current by early January, and any vendor missing a W-9 in that window becomes a backup withholding problem or an unfiled 1099. A vendor list that was never reconciled during the year turns January into a scramble of chase emails. The W-9 collected at onboarding is the document that makes January boring, which is exactly what a well-run vendor compliance program should aim for.

General information, not tax advice. Confirm current IRS thresholds with your accountant.