The Centralized Authorization File (CAF) number is a unique nine-digit identification number assigned to an individual representing a taxpayer before the IRS.
The CAF Number has the following format (9999-99999R).
The CAF number is assigned the first time a person submits an IRS Form 2848 (Power of Attorney and Declaration of Representative). The IRS mails a letter to the individual confirming their assigned CAF Number.
Once the individual is assigned a CAF number, any future Forms 2848 submitted by that individual should include their CAF number.