What is a CAF number? A CAF number is a unique nine-digit identification number and is assigned the first time you file a third party authorization with IRS. A letter is sent to you informing you of your assigned CAF number. Use your assigned CAF number on all future authorizations. Ability to Modify Authority The Centralized Authorization File (CAF) allows the input of codified additional acts authorized on a Form 2848, Line 5a. Taxpayers should be clear with regard to additional acts authorized and to which representative it applies. CAF Unit Addresses, Fax Numbers, and State Mapping General Rule: All states west of the Mississippi process authorizations in Ogden; all states east of the Mississippi process authorizations in Memphis. Exceptions: Louisiana and Arkansas process in Memphis; Wisconsin process in Ogden and International authorizations are processed in Philadelphia. Common Reasons for Power of Attorney (POA) Rejection Avoid problems when filing Form 2848, Form 8821, and Form 706. Frequently Used Forms and Publications Links to frequently used forms and publications. Third Party Authorization Purpose Third party authorization information. Other Third Party Authorization Third Party Designee, Oral Tax Information Authorization, Oral Disclosure Consent, and Publication 4019.