A Centralized Authorization File (CAF) number is a nine-digit number the IRS assigns the first time you file a third-party authorization, such as Form 2848 (Power of Attorney) or Form 8821 (Tax Information Authorization). It identifies you as an authorized representative.

Secure messaging uses your CAF number to determine which taxpayers' cases you can discuss, so every message is tied to an active authorization on file.

1. Select Link this CAF number above, or go to Your profile and choose CAF numbers.
2. Verify the CAF number and the name and address the IRS has on file for it. They must match your CAF record exactly.
3. Answer the identity confirmation questions. Most requests are confirmed within one business day.

Once linked, the CAF number appears in the selector on this page and its messages load automatically.

Messages appear only when all of the following are true:

• Your authorization (Form 2848 or 8821) for that taxpayer is active and recorded on the CAF you selected.
• The IRS office handling the case has started a secure-message conversation, or you've started one from the taxpayer's page.
• The tax matters and periods on your authorization cover the case being discussed.

If an authorization was filed recently, allow up to two weeks for it to be recorded.

Attorneys, CPAs, enrolled agents, and other representatives with an active CAF number can use secure messaging after linking the CAF number to their Tax Pro Account and verifying their identity.

Each linked CAF number keeps its own inbox, so firms with multiple office locations can keep casework separate.