Find out what you need to do if you have lost or misplaced your Employer Identification Number (EIN). 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.If you are unfamiliar with the online Employer Identification Number (EIN) application process, review these questions and answers. This confirmation letter is known as Form CP 575 and is mailed to the address mentioned in your Form SS-4 application. 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. This article will cover everything you need to know about EINs and what to do if you lose your EIN confirmation letter from the IRS. You will receive a 16-digit confirmation number as proof of filing.