Form W-9 requests a taxpayer identification number (TIN), which may be a Social Security number (SSN), an Employer Identification Number (EIN), or another valid TIN. This page explains why this information is required and how it is used in U.S. tax reporting.
The Purpose of a Taxpayer Identification Number
A taxpayer identification number is used to identify a person or entity for federal tax purposes.
On Form W-9, the TIN allows the requester to accurately report payments and match those payments to the correct taxpayer.
Why an SSN or EIN Is Required on Form W-9
Form W-9 is used in situations where U.S. tax reporting or withholding rules apply.
The SSN or EIN provided on the form allows the requester to comply with information reporting requirements and determine whether withholding applies.
Which TIN Is Used on Form W-9
The type of TIN requested on Form W-9 depends on the taxpayer’s classification.
- Individuals generally provide a Social Security number (SSN).
- Businesses and other entities generally provide an Employer Identification Number (EIN).
The form itself does not determine which TIN a taxpayer must have; it only requests the appropriate identifying number for reporting purposes.
How the TIN Is Used After Form W-9 Is Provided
After Form W-9 is provided, the requester retains the form as part of their records.
The TIN may later be used to prepare information returns, such as Forms 1099, that report payments made to the payee.
Form W-9 and Backup Withholding
Providing an incorrect TIN or failing to provide a required TIN may affect how payments are handled under U.S. withholding rules.
This connection is explained further in backup withholding explained .
Form W-9 Is Not Submitted to the IRS
The SSN or EIN provided on Form W-9 is given to the requester, not filed with the Internal Revenue Service by the individual or entity completing the form.
The requester uses the information only for authorized reporting and withholding purposes.
Related Clarifications
Official Reference
For the official form and IRS-issued instructions, see the official Form W-9 reference.