A W-9 is an IRS form (Request for Taxpayer Identification Number and Certification) that self-employed individuals, freelancers, and independent contractors provide to clients before receiving payment. The form collects your legal name, business name (if applicable), taxpayer identification number (usually your Social Security Number or EIN), and tax classification. Clients use the information on your W-9 to prepare and issue a 1099-NEC at year-end if they paid you $600 or more. You do not submit the W-9 to the IRS; it goes directly to the client and stays in their records.