Form W-9 is a request for a taxpayer identification number and certification, used by a US person - a citizen, tax resident or US-formed entity - to give their details to a payer. It carries a certification of US status signed under penalty of perjury and is provided to the payer rather than filed with the IRS.
Why does W-9 matter for founders?
A US EIN does not make a foreign owner a US person. A foreign-owned single-member LLC is generally disregarded to its foreign owner, so a W-8 form is usually appropriate rather than a W-9. Signing a W-9 certifying US status you do not have is a false certification.
Where can I read more about W-9?
Note: A plain-English definition for orientation, not legal or tax advice. Rules change - last checked 2026-07-21.