What Is a CAF Number? Uses, How to Get One, and Renewals

A CAF number, short for Centralized Authorization File number, is a nine-digit identifier the IRS assigns to tax professionals and other third parties who represent taxpayers or receive their confidential tax information. You do not apply for one directly. The IRS issues it automatically the first time you submit an authorization form, or in real time when you file your first authorization through the IRS Tax Pro Account online portal. Once assigned, the number is yours permanently and links to every taxpayer authorization on your record.

What the Number Actually Does

The Centralized Authorization File is the IRS database that tracks who is authorized to act for which taxpayers, on which tax matters, and for which tax years. Your CAF number is the key into that record. When an IRS employee looks it up, they see every active authorization tied to you and the scope of each one, so they can confirm your authority without asking you to re-fax paperwork on every call.¹

The IRS can assign a CAF number to an individual or to a business entity. Attorneys, CPAs, enrolled agents, and other authorized representatives all use them. At a firm, each representative gets their own number rather than sharing one.

How It Differs From a PTIN, TIN, or EIN

A CAF number is not the same as a Preparer Tax Identification Number, Taxpayer Identification Number, or Employer Identification Number. A PTIN identifies you as someone who prepares tax returns for compensation. A CAF number identifies you as someone authorized to represent a taxpayer or receive their confidential information. Many practitioners hold both, but they serve different functions.²

When You Need One

You need a CAF number whenever you submit a third-party authorization that the IRS will record on the CAF database. Two forms account for most of them:

Form 2848, Power of Attorney and Declaration of Representative, which authorizes you to represent a taxpayer before the IRS, speak on their behalf, sign agreements, and receive confidential tax information.
Form 8821, Tax Information Authorization, which authorizes you to inspect or receive a taxpayer’s confidential information but does not give you the right to represent them.

The CAF system also records authorizations from Form 706 estate tax returns, oral disclosure consents, and third-party designee checkbox authority granted on certain returns.³

One boundary matters here. If you or your client checks the “Specific Use” box on Line 4 of either form, the authorization is not loaded to the CAF database, and you will need to present a signed copy each time you contact the IRS about that matter. Specific use covers items without a standard tax form and period pairing, such as applications for employer identification numbers, Form 2553 S-corporation elections, and W-2 or 1099 information return matters.⁴

How to Get a CAF Number

There is no standalone application. You receive a CAF number as a byproduct of filing your first authorization. Three routes exist, and the speed differences are significant.

Tax Pro Account

The IRS Tax Pro Account processes Power of Attorney and Tax Information Authorization requests in real time, with no paper forms. Once the taxpayer approves your request through their own IRS online account, the authorization appears on the CAF database immediately. If you do not already have a CAF number, Tax Pro Account assigns one during this process.⁵

The limitation: Tax Pro Account currently handles only individual taxpayer authorizations. For business entities, you still submit Form 2848 or Form 8821. The individual client must also have a U.S. address and be able to sign in to their own IRS online account to approve the request.⁵

Online Form Upload

If Tax Pro Account will not work for your situation, you can upload a completed Form 2848 or Form 8821 through the IRS online submission portal. The file must be PDF, JPG, or GIF, up to 15 MB. Electronic signatures are accepted through this portal, including typed names, scanned images of handwritten signatures, and signatures created through third-party software. If you have no personal or business relationship with the taxpayer and they sign electronically in a remote transaction, the IRS requires identity authentication for the taxpayer before the form is accepted.⁶

Fax or Mail

You can also fax or mail the completed form. Submissions by fax or mail must carry a wet ink signature; the IRS does not accept electronic signatures on these.⁶ The destination depends on where the taxpayer lives, and fax numbers can change without notice, so check the current addresses in the Form 2848 instructions before sending.⁷

Filling Out the Form the First Time

When completing Form 2848 or Form 8821 before you have a CAF number, enter “NONE” in the CAF number field. The IRS will assign your number when it processes the form and send you a letter with the number.² You will also need to provide your name, mailing address, PTIN if applicable, and phone number, along with the taxpayer’s name, identification number, address, and the specific tax matters and periods the authorization covers.⁷

How Long Processing Takes

Tax Pro Account authorizations post immediately. All other submissions are worked first-in, first-out with an IRS target of 5 business days.⁸ In practice, processing has stretched well beyond that during backlogs, with the Taxpayer Advocate Service reporting wait times ranging from roughly three weeks to over two months in recent years.⁹ If speed matters and your client is an individual, Tax Pro Account is the clear winner.

Using the Number Once You Have It

Enter your CAF number on every future Form 2848 and Form 8821 you file. The IRS links each new authorization to your existing CAF record, so you never apply again.²

When you call the IRS about a client’s account, give the assistor your CAF number so they can verify your authorization and confirm which tax matters and periods you are cleared to discuss.¹

How Long Authorizations Last

A Power of Attorney filed on Form 2848 stays in effect until you withdraw it or the taxpayer revokes it. There is no automatic expiration.¹

Form 8821 Tax Information Authorizations work slightly differently for future tax years. You can list current and past periods without restriction, but the IRS will not record future tax periods that extend more than three years beyond December 31 of the year the form is received.¹⁰

Filing a new Form 2848 for the same tax matter and period generally revokes any earlier power of attorney already on file for that matter. It does not revoke any Form 8821 covering the same taxpayer.¹¹

If You Lose Your CAF Number

Your CAF number appears on the acknowledgment letter the IRS sent when it processed your first authorization, and on copies of any prior Forms 2848 or 8821 you have on file. If you cannot find it, call the Practitioner Priority Service at 866-860-4259. Retrieving a forgotten or lost CAF number is a standard PPS service, and the assistor can give it to you after verifying your identity.¹²

1
Internal Revenue Service. Power of Attorney and Other Authorizations
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Internal Revenue Service. What Is a CAF Number?
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Internal Revenue Service. Command Codes CFINK, RPINK, KAFFQ and KAFTQ for CAF Inquiry
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Internal Revenue Service. Processing Third-Party Authorizations onto the Centralized Authorization File (CAF)
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Internal Revenue Service. Tax Pro Account
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Internal Revenue Service. Submit Forms 2848 and 8821 Online
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Internal Revenue Service. Instructions for Form 2848
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Internal Revenue Service. 3.30.123 Processing Timeliness – Cycles, Criteria and Critical Dates
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Taxpayer Advocate Service. The IRS Hasn’t Processed My Power of Attorney Form. Should I Submit Another?
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Internal Revenue Service. Instructions for Form 8821
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Internal Revenue Service. Instructions for Form 2848 Power of Attorney and Declaration of Representative
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Internal Revenue Service. Practitioner Priority Service