The hours of operation are 7 a.m. This EIN confirmation letter is called CP 575, and the IRS only mails the letter to the mailing address listed on line 4 of the SS-4 application.The only two ways to get an EIN Verification Letter (147C) is to call the IRS at 1-800-829-4933, or to mail the IRS a written request. EIN confirmation letter is typically a tax ID certificate. How to fill out the Employer Identification Number Confirmation Guide? Once the application has been validated, you will get a digital copy of your EIN confirmation notice. You can download and print this letter as needed. Fill out IRS form SS4 and mail it to the IRS. Unable to verify the vehicle identification number above. The type of entity in the space provided.