To ensure that provider information is correct, as of January 1, 2017, Regence will require all providers to submit a 147C letter upon initial credentialing and recredentialing. The information on a 147C letter documents how an individual or business entity is filed with the Internal Revenue Service (IRS), and should match the information on business tax returns and 1099-K forms. The best way to request a 147C letter is to contact the IRS by phone at 1 (800) 829-4933. The IRS will fax a copy of what is on file for your business. It is recommended to call the IRS at your earliest convenience to obtain your 147C letter.