What is a W-9, and why do clients ask for one?

Form W-9 is a request for taxpayer identification. A business that pays you as a non-employee needs your legal name, business name if different, entity type, address, and taxpayer identification number, which is either your Social Security number or your EIN. They keep the form in their records and use it to issue a Form 1099-NEC at year end reporting what they paid you. The W-9 itself is never filed with the IRS, which is worth knowing because it means the form exists purely to transfer information to the payer.

Providing an EIN rather than a Social Security number is worth doing if you have one. Every client who pays you holds this form, often indefinitely and sometimes in systems of unknown security, and each copy is another place your personal identifier exists. An EIN is free from the IRS and serves the same purpose here. Sole proprietors can obtain and use one even without employees.

Two consequences of getting this wrong. Declining to provide a W-9, or providing an incorrect taxpayer identification number, obligates the payer to apply backup withholding, currently 24 percent of each payment sent to the IRS on your behalf, which you recover only when you file. And be alert to fraud: W-9 requests are a common phishing vector precisely because the form contains a taxpayer identification number and address, so confirm the requester is a business you actually work with, and send it through a secure channel rather than plain email where practical. Legitimate requests come before or shortly after work begins; an unexpected W-9 request from an unfamiliar party deserves verification.