What this notice is about We received your Form 2848, Power of Attorney and Declaration of Representative, Form 8821, Tax Information Authorization, or Form 706, U.S. Estate Tax Return, and we assigned you a Centralized Authorization File (CAF) number. What you need to do Keep this notice so you know what your CAF number is for all future third party authorization requests and telephone contacts with the IRS on behalf of the taxpayer. You may want to Keep your CAF number in a safe place for future reference. Notify the IRS if this was assigned without your knowledge. Frequently asked questions What is a CAF number? A CAF number is a unique nine-digit identification number that we assign to you the first time you file a third-party authorization with the IRS. We send a CP547 notice to you informing you of your assigned number. Use your assigned number on all future authorizations. If we assigned you more than one CAF number and you didn’t specifically request more than one, please fax a copy of each CP547 notice you received to the fax number in the notice using either a fax machine or an online fax service. Protect yourself when sending digital data by understanding the fax service’s privacy and security policies. What should I do if I don’t remember my CAF number? If you’re a tax professional and can’t remember your CAF number, you can call the Practitioner Priority Services (PPS) at 866-860-4259. Once authentication is verified for the client and representative, your CAF number can be provided over the phone. If the Customer Service Representative (CSR) is unable to authenticate you as the owner of the CAF number, a 1727C Letter will be issued to the CAF address of record for the representative. Reference Tools Publication 1, Your Rights as a Taxpayer Full list of tax forms and instructions Need Help? You can authorize someone to contact the IRS on your behalf. See if you qualify for help from a Low Income Taxpayer Clinic. If you can’t find what you need online, call the IRS number at the top of your notice or letter. If you didn’t receive a letter or notice, use telephone assistance. If you can't resolve the penalty on your own, contact Taxpayer Advocate Service, an independent organization within IRS.