Form W-9 is a really simple IRS form with precisely one function. It lets you send your Tax Identification number (TIN)—which is your Employer Identification Number (EIN) or your Social Security number (SSN)—to another person, bank, or other financial institution.

The W-9 is a straightforward “information return,” meaning it’s just for giving someone else a piece of information they need (rather than the IRS). But because you’re not sending it to the IRS, you need to be careful about who exactly you send it to.

How to fill out a W-9
When you hear that you need to fill out a W-9, you might think it will be a complicated tax form. The good news here is that filling out a W-9 is a fairly short form.
See how to fill out a W-9 in these steps.

On the top of W-9 tax form:
Write the name as shown on your income tax return.
Write the business name/disregarded entity name if different than above.
Fill out the federal tax classification for the person whose name is entered on line
1. Only one box should be checked.
Include any exemption codes, if applicable.

Write the business’ address (number, street and apartment number or suite number).
Write the business’ city, state, and zip code.
List account numbers, if applicable.