CAF number: how practitioners get one, find a lost one, and keep it in good standing

What a CAF number is and is not

The Centralized Authorization File is the IRS database that records powers of attorney (Form 2848), tax information authorizations (Form 8821) and certain Form 706 authorizations against the taxpayer's account. IRM 21.3.7.1.13 describes it as the system that “assigns a unique identifying number to the taxpayer’s authorized representative(s) on Form 2848” and maintains the data “in relation to the appropriate taxpayer accounts and tax modules.” When you call the Practitioner Priority Service or pull a transcript through the Transcript Delivery System, the employee or system checks the CAF, not the paper form.

The number identifies you; it does not credential you. The procedural regulations are explicit: “The issuance of a CAF number does not indicate that a person is either recognized or authorized to practice before the Internal Revenue Service.” (26 CFR 601.506(d)(2).) The Form 2848 instructions say the same thing more briefly: “The CAF number is not an indication of authority to practice.” Your authority comes from your status under Circular 230 (see who can represent a taxpayer) and from a valid authorization for the specific taxpayer, form and period.

A CAF number is also different from your other identifiers. IRM 21.3.7.3 says CAF numbers are “different from the third-party's Taxpayer Identification Number (TIN) or Preparer Tax Identification Number (PTIN).” Two structural rules follow from the same section: “A Form 2848 representative can only be an individual,” while a Form 8821 designee can be an individual or a business entity. That is why a firm can hold a business CAF number for Form 8821 work but every representative on a Form 2848 needs a number in his or her own name.

The number is not a required element of either form. The regulation states that an authorization “which does not include such number will not be rejected based on the absence of a CAF number,” and IRM 21.3.7.5.1 lists clear identification of the third party as the essential element, noting “A CAF number is not required.” Leaving it blank or writing “None” simply tells the CAF unit to look you up or assign one.

How a CAF number gets assigned

There are two routes.

On paper, the Form 2848 instructions tell you to enter your nine-digit CAF number on line 2 or, if none has been assigned, to “enter “None,” and the IRS will issue one directly to the” representative. Before assigning a number, the CAF examiner must search for you by name. IRM 21.3.7.3.1 tells employees to research command code RPINK first because “This will prevent assigning a number in error,” and the system now blocks a second number for a representative with the same name and address. If your name or address is misspelled or illegible, the examiner is told not to assign a number and to return the authorization.

IRS systems display the number as four digits, a hyphen, five digits and an “R” (the IRM's example message reads “Representative Added NNNN-NNNNNR”). The CP 547 notice, titled “We Assigned You a Centralized Authorization File (CAF) Number,” is generated when a new number is issued (IRM 21.3.7.14). The IRS page on Tax Pro Account adds that Letter 1727C is mailed when the CAF number is assigned after your first authorization on Form 2848 or 8821, so keep whichever document you receive with your practice records.

Tax Pro Account can assign an individual CAF number immediately. A business number still requires a form: the IRS page says “To get a CAF number for a business, submit Form 2848 or 8821.” See Tax Pro Account for the full workflow.

Processing time for paper and uploaded forms is not fixed. IRM 21.3.7.1.10 says receipts are processed “first in first out (FIFO), regardless of the method used to submit the authorization,” and points to the Processing Status for Tax Forms page on IRS.gov for current timing. If you need to act before the form posts, the IRS page on online submission says you can fax the signed form to the employee handling the case or contact PPS.

Where the CAF units are: fax numbers and addresses

Three CAF units process authorizations, and the one that receives a form depends on the taxpayer's address, not yours. The Where To File Chart in the Form 2848 instructions (Rev. September 2021, checked against the IRS.gov About Form 2848 page in October 2026 and still the current revision) gives these destinations. Address-change letters and merge requests go to the unit where you filed your authorizations, using the same numbers and addresses.

The instructions warn that “These numbers may change without notice. For updates, go to IRS.gov/Form2848 and search under “Recent Developments.”” As of October 2026 the only item posted there is a July 2026 note on entries that make an authorization “modified”; it does not change the chart. That note matters for another reason: a Form 2848 is recorded as modified when line 5a grants anything “other than disclosure to third parties, substitute or add representative(s), or sign a return,” or when line 5b limits the representative's authority, and representatives on a modified authorization cannot use TDS or set up an installment agreement in Tax Pro Account for those periods. If a form is for a specific use under line 4, it does not go to a CAF unit at all; it goes to the office handling the matter.

Multiple numbers, locations and merges

You are not limited to one number. IRM 21.3.7.3 allows a third party to “request multiple CAF numbers to differentiate between multiple office addresses” and also to differentiate between related entities. The request must be separate and in writing, and must include your name and any name variations with a dated signature, your existing CAF numbers and addresses, and the additional numbers and addresses requested.

Duplicate numbers created by accident can be merged, but only on your written request. IRM 21.3.7.3.3 says “CAF merges will only be performed if you receive direct contact from the representative and the request must be in writing,” and only technical leads may approve and perform them. Your letter should identify the number to keep and the numbers to merge, and attach any CP 547 or Letter 1727C you hold for the numbers, since the technical lead's approval package includes “Any notices or letters, e.g., CP 547, that are attached to the representative’s merge request.” The name and name control on each record must match before the merge can run; if they do not, the IRS corrects the name first. The CAF unit then sends Letter 1727C confirming the surviving number. Only the numbers listed in your request are merged, so list all of them.

Sign and date the letter and send it by fax or mail to the CAF unit where you filed your authorizations (see the unit table). The merge section itself says only that the request “must be in writing,” but the same units process representative record changes only when “Signed and dated correspondence is received by fax or mail,” and the IRM tells phone assistors that written correspondence is needed before any record update is processed. Tax Pro Account has no merge function; the IRS page says “If you have more than one CAF number, you may link them all,” which makes each visible in one profile but does not combine them.

Keeping your CAF record current

Notice copies and refund checks authorized on a Form 2848 go to the address on your CAF record, so stale data has consequences. IRM 21.3.7.4.1 says the CAF unit updates a representative's name, address, telephone or fax number when the “Check if new” box is marked on line 2 of a Form 2848 or 8821, or when signed and dated correspondence specifically requests the change. A phone call is not enough; the IRM tells telephone assistors to advise the representative that “written correspondence must be obtained to process the updated information request.” The Form 2848 instructions likewise say the IRS does not require a new Form 2848 for an address change; a signed written notice sent to where you filed the form is sufficient. The IRM accepts the request “via mail, fax (EFS) or TDC,” that is, by mail or fax to the CAF unit or through the online upload tool, and the IRS Tax Pro Account page spells out the letter route: “Sign and date a written notification of address change. Mail or fax it to the location where you filed the Form 2848 or Form 8821.” Use the fax number or address for your CAF unit from the unit table; the IRM's trigger for the update is “Signed and dated correspondence,” so sign and date it.

Two details matter. If your address shows both a street address and a PO box, the CAF unit will process only the PO box. And address information cannot currently be updated inside Tax Pro Account; the IRS page says to use a form with the box checked or a signed written notice.

If IRS mail to you comes back undeliverable, IRM 21.3.7.12 has the CAF unit check whether the authorization is still valid, correct the address if it can, and otherwise write to the taxpayer for your current address and put a “U” code on your record. The IRM notes that the “U” indicator is removed once new information arrives so that you receive authorized notice copies again. When undeliverable mail indicates a representative has died, the record is marked with an “E” indicator for deceased.

Recovering a lost or forgotten number

1. Check your files for CP 547 or Letter 1727C, or a prior Form 2848 or 8821 on which the number was entered.
2. If you have a client issue to discuss, call PPS at 866-860-4259. The IRS page on CAF numbers says a PPS assistor “will initiate the process to help you retrieve your CAF number once you provide your authenticating information.”
3. Expect the number to be mailed if the call cannot support oral disclosure. IRM 21.1.3.3 tells assistors to give the number verbally only after verifying your name and full street address, and not to give it at all if you cannot be authenticated or are “calling solely to obtain the CAF number without a client-related issue.” In that case Letter 1727C goes to your address of record.
4. You can also write to the CAF unit. Under IRM 21.3.7.3.2 the unit confirms the number exists for the name and address provided and sends Letter 1727C.

Linking your CAF number in Tax Pro Account

Linking associates your CAF number with your own TIN so that Tax Pro Account can show every active authorization recorded under that number, including ones filed on paper. The IRS page explains that an individual CAF number links to your SSN or ITIN and a business CAF number links to the business EIN, and that you cannot cross them. Linking is a one-time step and the number cannot be unlinked.

IRM 21.2.1.63 describes the mechanics: you request a PIN, which is mailed to your CAF address of record and is valid for 30 calendar days; if it does not arrive you must wait 14 calendar days from issuance before requesting a replacement. Once linked you can view your client list, view each taxpayer's authorized modules and withdraw from authorizations in real time. A business number must be linked by a person with authority to associate it with the EIN (the IRS page names a designated official or sole proprietor).

Pending review and compromised numbers

Because stolen CAF numbers have been used to file fraudulent authorizations, the CAF function can freeze a number. The IRS page on CAF numbers says that when it identifies potential harmful activity, “we may place your CAF number in “pending review” status while we conduct further research into the issue,” and that while the number is pending “The IRS will not process any forms or requests, including transcript, while the CAF number is in pending status.” If you receive a notice, respond quickly; the page says the length of the review depends on how long it takes to receive your response.

Internally, IRM 21.3.7.5.5.2 added two practice codes to the CAF record: “P” for pending (“Pending - “P” will suspend activity on a CAF number”) and “C” for a number confirmed as compromised. Forms that list a coded representative alongside other representatives in good standing are processed for the others. The same section shows these as “CAF STATUS: PENDING REVIEW” or “CAF STATUS: CONFIRM FRAUD” to any employee who researches you. Disciplinary status works the same way: the Office of Professional Responsibility notifies the Memphis CAF point of contact when a practitioner is suspended, disbarred or ineligible, and Forms 2848 signed by that practitioner are not processed (IRM 21.3.7.9.1 and 21.3.7.9.2).

Getting a list of your clients on the CAF

The CAF can produce a representative-by-representative listing of clients, called the CAF 77, showing taxpayers, TINs, form numbers, tax periods and SDLNs. IRM 21.3.7.11 says external requesters “may submit a written Freedom of Information Act (FOIA) request to receive a listing of their own clients,” using the sample CAF Client Listing Request language on the IRS FOIA pages. The IRM gives the mailing address as IRS GLDS Support Services, Stop 93A, Post Office Box 621506, Atlanta, GA 30362, fax 877-891-6035. If you have linked your number in Tax Pro Account, the same information is visible online.

Either list is the starting point for cleaning up stale authorizations, and there are two ways to do the cleanup. On paper, IRM 21.3.7.10.1 accepts “A listing of clients and respective TINs with a cover sheet requesting withdrawal by a third-party” so long as you provide a signed and dated written statement requesting withdrawal and clearly identify the clients; fax or mail it to your CAF unit. Online, once your CAF number is linked, Tax Pro Account shows every active authorization under Taxpayers, including ones filed on paper, and lets you withdraw from each one; the IRS page says “Once you withdraw, the authorization is immediately removed from the CAF database,” and IRM 21.2.1.63 says the client is then notified by CP 312 (individual) or CP 313 (business). The online route needs no FOIA request and no mail. For details and the difference between withdrawing and revoking, see revoking and withdrawing authorizations. For other FOIA work in a case, see getting the exam file through FOIA.

Questions practitioners ask