A US IRS form a business asks a contractor to complete, collecting their legal name and taxpayer ID so the business can later issue a 1099-NEC.
A W-9 is the IRS form a business asks you to fill out so they can report what they pay you. It collects your legal name, address, business structure, and taxpayer ID number — your SSN or EIN. No money changes hands; it’s just the information the payer needs to issue a 1099-NEC later.
For sellers, expect to send a W-9 to most business clients before your first payment. Using an EIN instead of your SSN keeps your Social Security number off documents that pass through client accounting departments. For buyers hiring contractors, collect the W-9 before you pay, not in January — chasing it down at tax time is a yearly headache.
A W-9 contains sensitive information, so send it through a secure channel rather than plain email when you can. If you’re unsure which tax-classification box to check or whether to use an SSN or EIN, confirm with a tax professional — it affects how your income is reported.