The 147c is a request from the IRS for an Employer Identification Number (E.I.N.) letter. If your company has been assigned an E.I.N., and lost it, this is what you would request for a replacement letter. You can request this by phone or mail. The number to call is as follows:1-800-829-4933;Requesting by mail, you can write to the address where you file regular returns. Be sure to write the words "Request for a 147c number" in the letter.