W-9 CP575 (click for an example)
A CP575 is a verification of your EIN that is produced at the time your EIN is issued. The form cannot be reproduced by the IRS. If you have lost your CP575, you can call the IRS and request letter 147C which is a verification of your EIN and legal business name by the IRS. Either a CP575 or a letter 147C is required by Medicare when enrolling as a group/supplier.
IRS Telephone Assistance for Businesses:
Toll-Free, 1-800-829-4933 Hours of Operation: Monday – Friday, 7:00 a.m. – 10:00 p.m. your local time (Alaska & Hawaii follow Pacific Time).