The Centralized Authorization File (CAF) is an IRS computer database system containing information regarding the authority of individuals appointed under powers of attorney. The system gives IRS personnel quicker access to authorization information without having to request the original document from the taxpayer or representative. It also enables the IRS to send the representative copies of notices and communications that are sent to the taxpayer.
A CAF number is the unique 9-digit identification number assigned to an individual the first time they file a third party authorization with IRS. The CAF number is only a pointer to the centralized file for authorizations that have been established for the individual. By itself, it doesn't indicate that the individual is either recognized or authorized to practice before the IRS.
An individual is issued a CAF when they are designated as a representative on either Form 2848, Power of Attorney and Declaration of Representative, or Form 8821, Tax Information Authorization, and "NONE" is indicated as the CAF number.
An individual who has forgotten their CAF can call the IRS Practitioner Priority Service for assistance in retrieving it.
Additional Information:
IRS: Publication 947, Practice Before the IRS and Power of Attorney