The W-8 and W-9 form families are the foundation of U.S. withholding tax compliance for supplier payments. Most AP teams know that some form of tax documentation is required before paying a new supplier. Fewer teams have a clear working knowledge of which form applies in which situation, what information must be present for the form to be valid, and what the compliance consequence is when the form is wrong.
This article is written for AP professionals who process supplier payments and need a practical working understanding of these forms, not a comprehensive tax treatise. For any specific determination affecting material payment amounts, consult a qualified tax professional.
W-9: The Domestic Baseline
Form W-9 is required for U.S. persons, including U.S. citizens, U.S. resident aliens, and U.S.-formed business entities. When a supplier submits a W-9, they are certifying their U.S. taxpayer identification number (TIN) and certifying that they are not subject to backup withholding (or explaining why they are exempt from it).
The AP team's obligation with a W-9 is straightforward: collect the form, verify the TIN format is valid (either a Social Security Number in XXX-XX-XXXX format or an Employer Identification Number in XX-XXXXXXX format), and retain it on file. If the TIN provided does not match IRS records and the IRS sends a "B-Notice," the organization must begin backup withholding at 24 percent until the issue is resolved.
A W-9 does not expire. A form collected from a supplier in 2019 is still valid unless the supplier's circumstances changed in a way that affects their tax status, such as a change in entity structure or a loss of U.S. person status. The practical standard most AP teams follow is to re-collect W-9s every three years as part of vendor master maintenance.
The W-8 Form Family: Which Form for Which Supplier
Foreign persons and foreign entities cannot submit a W-9. Instead, they submit one of several W-8 variants, each designed for a specific category of foreign payee.
Form W-8BEN is for foreign individuals. A foreign contractor who is a natural person, not a corporation or partnership, submits a W-8BEN. The form captures the individual's country of residence, any applicable treaty claim, and the treaty article and rate being claimed.
Form W-8BEN-E is for foreign entities, meaning corporations, partnerships, and other foreign business organizations. This is the form most commonly encountered in enterprise AP because most foreign suppliers are incorporated entities. The W-8BEN-E is substantially longer than the W-8BEN and includes sections specific to FATCA (Foreign Account Tax Compliance Act) status that must be completed correctly even for payments not otherwise subject to FATCA.
Form W-8ECI is for foreign persons with income effectively connected to a U.S. trade or business. If a foreign supplier has a permanent establishment in the United States or is conducting business activities in the United States in a way that causes their income to be effectively connected to a U.S. trade or business, they should submit a W-8ECI rather than a W-8BEN or W-8BEN-E. Income covered by a W-8ECI is not subject to the standard Chapter 3 withholding but may be subject to U.S. tax filing obligations.
Form W-8IMY is for intermediaries and flow-through entities, such as partnerships or trusts acting as intermediaries. This form is less commonly encountered in typical supplier payment workflows but is required when the payment recipient is not the beneficial owner of the income.
What to Review Before Accepting a W-8
Accepting an incomplete or incorrect W-8 is not a compliance workaround. If the withholding rate applied to a payment is based on a defective form, the withholding agent (your organization) remains liable for the correct withholding amount.
For a W-8BEN-E, the minimum required fields for Chapter 3 purposes are: the entity's legal name matching the name on the invoice, the country of incorporation or organization, the Chapter 3 status (corporation, partnership, disregarded entity, etc.), and a certification signature. If the entity is claiming a treaty benefit, the treaty country, the treaty article, and the rate being claimed must also be present.
Common errors that require follow-up with the supplier before the form is accepted: the treaty benefit section is left blank even though a reduced rate is being applied, the signature is dated more than three years prior to the payment date (W-8 forms expire after three years), the entity name does not match the invoicing entity, or the FATCA classification chapter 4 section is entirely blank rather than completed with the correct entity classification.
Validity Period and Re-Collection
W-8 forms have a validity period of three years from the date of signature, or until the last day of the third succeeding calendar year. A form signed on March 15, 2022, expires on December 31, 2025. After expiration, the withholding agent can no longer rely on the treaty claims made in the form and must either collect a new form or apply the default withholding rate of 30 percent for the income type.
The practical consequence for AP teams: if your vendor master contains W-8 forms collected during a vendor onboarding process several years ago and they have not been re-collected, some portion of your foreign vendor records have expired documentation on file. Payments processed against expired documentation carry withholding compliance risk, particularly if the expired form contained a treaty exemption claim.
When No Form Is Collected
If a payment to a foreign payee is made without a valid W-8 form on file, the default withholding rate applies. For most payments to foreign corporations, the default rate under Chapter 3 is 30 percent of the gross payment amount. For payments to foreign individuals, the same 30 percent rate applies unless the income type carries a different default rate.
This is not a case where the organization can decide to take the risk and pay without withholding. The withholding obligation is the organization's, not the supplier's. If the organization pays the gross amount without withholding and no valid W-8 is on file, the organization owes the IRS the withholding amount that should have been deducted, plus interest and potentially penalties.
We are not saying that every payment to a foreign supplier will result in 30 percent withholding in the absence of a W-8. Many payments to foreign suppliers for goods purchased outside the United States, or for certain categories of services, are not subject to Chapter 3 withholding at all. The withholding determination depends on the nature of the payment, the source of the income, and the income category. That determination needs to be made explicitly, not by assuming no withholding applies because no one raised the question.
The forms themselves are available from the IRS website. The instructions accompanying each form are detailed and provide guidance on which form to use and how to complete it. For AP teams that process meaningful volumes of international payments, building familiarity with the W-8 form family and maintaining a systematic process for collection, review, and re-collection is one of the highest-leverage compliance investments available.