Line 2 of Form 2848 asks the representative for a "CAF No." and it stops people cold the first time they file one — particularly new preparers, who reasonably assume it is a number they were supposed to already have. It is not. The CAF number is issued because you filed, not before, and the correct entry on a first filing is a word rather than a number. This is not tax advice; the IRS page on CAF numbers and the Form 2848 instructions are the authority.
A CAF number is a nine-digit number the IRS assigns to a representative to track the authorisations they hold. It appears on Form 2848 line 2 and identifies you across every client you represent. If you have never been assigned one, write "None" — the IRS issues one in response to your first accepted Form 2848 or 8821.
What does CAF actually stand for?
Centralized Authorization File. It is the IRS's index of who is authorised to act for, or receive information about, which taxpayers. Every Form 2848 (Power of Attorney and Declaration of Representative) and every Form 8821 (Tax Information Authorization) that the IRS accepts gets recorded there, filed under the representative's CAF number.
The practical effect is that the number is about you, not about a client. One CAF number covers your entire book. When you call the Practitioner Priority Service and are asked to identify yourself, this is the number that lets the agent see, in one lookup, that you hold a valid authorisation for the taxpayer you are calling about.
Is it the same as my PTIN or EIN?
No, and confusing them is the most common line-2 error. Four different numbers do four different jobs:
- CAF number — tracks the authorisations you hold. Line 2 of Form 2848.
- PTIN — identifies you as a paid return preparer, and appears on returns you prepare. Renewed annually.
- EIN — identifies your firm as an entity for employment and business tax purposes.
- SSN or ITIN — identifies you as an individual taxpayer.
Only the CAF number belongs in the CAF box. A PTIN entered there does not fail loudly; it produces a mismatch that surfaces later, when someone is trying to reach you about a client and cannot.
How do I get a CAF number?
You do not apply for it separately. You get one by filing your first authorisation:
- Complete Form 2848 or Form 8821 for a real client, in full.
- Write "None" in the CAF number box. Not zeros, not a placeholder, not your PTIN — the word tells the IRS to assign one.
- Submit it through the channel the IRS currently specifies for that form.
- Wait for the notice. The IRS assigns the number and notifies you, typically within a few weeks. From then on it goes on every subsequent authorisation.
Unlike the PTIN, the CAF number does not expire and is not renewed annually. You are assigned one, once, and you keep it.
Where exactly does it go on Form 2848?
In Part I, section 2, in the block identifying each representative — alongside the representative's name, address, PTIN, telephone and fax. If you are naming more than one representative, each gets their own line with their own CAF number; they are not shared across a firm even when the firm files everything centrally.
The rest of the form is where the actual scope lives: section 3 defines the tax matters and periods you are authorised for, and section 5 is where you add or strike specific acts. Getting the CAF number right does nothing for you if section 3 is drawn too narrowly — the number identifies you, the matter description is what you are allowed to do. We walk through the whole form in the guide to IRS Form 2848.
Do I need a CAF number for Form 8821 as well?
Yes — the same number, the same box, a different level of authority. Form 8821 lets you receive a taxpayer's information; Form 2848 lets you act for them. Both are recorded against your CAF number, which is why a representative's CAF record shows a mix of the two. If all you need is transcript access, the lighter form is usually the right one, and we compare them in the guide to Form 8821.
How do I stop retyping my own details on every 2848?
This is the practical shape of the problem for a practice: the representative block — your name, address, CAF number, PTIN, phone — is identical on every Form 2848 you will ever file. The taxpayer block changes every time. So does the matter description. Filing by hand means retyping your own constants for each new client, which is exactly where a transposed CAF digit comes from.
Filly is built around that split: your firm's details live in one reusable profile, each client lives in their own, and a form is filled from both with a review step before it goes out. The same client profile then carries into the rest of the engagement — the power of attorney, an affidavit, a Form 9423 collection appeal if the matter goes that way. Signature goes out as a no-login e-sign link, so a client signs from a phone without creating an account. Free covers 3 forms, 5 clients and 10 fills a month with no card.
FAQ
I have a CAF number but cannot find it. How do I look it up?
Call the IRS Practitioner Priority Service and ask, after identifying yourself. Do not file a fresh authorisation with "None" to get a new one — that risks a duplicate record, which is harder to clean up than the phone call.
What does a CAF number look like?
Nine digits. It is not formatted like an SSN and carries no embedded meaning; it is a sequential identifier the IRS assigns.
Can an unenrolled preparer get a CAF number?
The number itself is administrative, but who may represent a taxpayer is governed separately, and unenrolled preparers have limited representation rights. Check your standing under the current IRS rules before you file a 2848 naming yourself — the Declaration of Representative in Part II is where you certify the basis on which you may act.
Does my firm need its own CAF number?
CAF numbers are assigned to individuals who represent taxpayers, not to firms in place of individuals. Each representative named on a Form 2848 carries their own.
Does the CAF number change when an authorisation is revoked?
No. Revoking a Form 2848 removes that authorisation from the file; your number persists and continues to carry everything else you hold.
What happens if I put the wrong number on line 2?
Usually nothing dramatic at filing — and that is the problem. The authorisation may be recorded against the wrong identifier or not linked to you at all, so it surfaces later as an agent who cannot see your authority when you need it. Verify the digits before signing, not after a call goes wrong.