Noun
W-9 (plural W-9s)
(US, taxation) A form to declare that someone is a U.S. tax payer.
Copyright Owners' FAQCopyright Clearance Center's Royalty Payment PoliciesCopyright Clearance Center's Royalty Payment PoliciesWhy did I receive a request for an IRS Form W-9 or W-8 from Copyright Clearance Center? Source: Internet
Each winner must sign a W-9 form. Source: Internet