Form W-9 (Subcontractors)

Use Form W-9 to provide your correct Taxpayer Identification Number (TIN) to the person who is required to file an information return with the IRS to report, for example:

Income paid to you.
Real estate transactions.
Mortgage interest you paid.
Acquisition or abandonment of secured property.
Cancellation of debt.
Contributions you made to an IRA.

https://www.irs.gov/pub/irs-pdf/fw9.pdf