CARC 55 appeal letter template — Experimental/Investigational Procedure, Treatment, or Drug
CARC 55 means the payer has classified the billed procedure, treatment, or drug as experimental or investigational and therefore not covered. This template helps staff draft an appeal challenging that classification with supporting clinical evidence.
When to appeal vs. correct & resubmit
Appeal when you believe the service is supported by peer-reviewed literature, has an established CPT/HCPCS code and standard-of-care use, is FDA-approved/cleared for the billed indication, or when the payer's own policy criteria for coverage were actually met. Correct and resubmit instead if the claim was coded incorrectly, if a more accurate code exists for a non-experimental alternative, or if documentation simply omitted required medical necessity details unrelated to the experimental designation.
Appeal letter template
Copy the template, replace every [bracketed] field with your details, and keep only the paragraph that fits your situation.
[Date] [Payer Name] Appeals Department [Payer Address] Re: Appeal of Denial — CARC 55 (Experimental/Investigational) Patient Name: [Patient Name] Member ID: [Member ID] Claim #: [Claim #] Date(s) of Service: [DOS] Provider: [Provider Name, NPI] Procedure/Service: [CPT/HCPCS] Authorization #: [Authorization #] Dear Appeals Reviewer, This letter is a formal appeal of the above claim, which was denied under CARC 55, indicating the procedure/treatment/drug was deemed experimental/investigational by the payer. We respectfully request reconsideration of this determination for the following reasons: 1. The billed service, [CPT/HCPCS], is a recognized, established procedure/treatment with [FDA approval status / standard CPT or HCPCS coding / published clinical guidelines — describe here]. 2. Supporting clinical documentation, including [provider notes, treatment history, relevant literature], demonstrates that this service was medically appropriate and consistent with accepted standards of care for the patient's diagnosis. 3. [If applicable: Prior authorization #Authorization # was obtained and/or the payer's own medical policy criteria for this service were met — see attached documentation.] 4. We ask that the payer provide the specific medical policy or criteria relied upon to classify this service as experimental/investigational so that we may fully address the basis for denial. We request that [Payer Name] reverse the denial coded CARC 55 and reprocess this claim for payment based on the enclosed documentation. Please contact our office at [Phone] or [Email] with any questions or if additional information is needed. Thank you for your prompt attention to this matter. Sincerely, [Provider Name, NPI] [Practice Name] [Phone] [Email]
What to attach
- Copy of EOB/ERA showing CARC 55 denial
- Relevant medical records and chart notes supporting medical necessity
- Prior authorization confirmation or reference number, if obtained
- Peer-reviewed clinical literature or treatment guidelines supporting non-experimental status
- FDA approval/clearance documentation for the drug or device, if applicable
- Payer's medical policy document, if available, for the service in question
Frequently asked questions
What does CARC 55 mean?
It means the payer has determined that the billed procedure, treatment, or drug is experimental or investigational and therefore does not meet their coverage criteria.
Can an experimental/investigational denial be successfully appealed?
It is possible if you can provide evidence such as FDA approval status, established CPT/HCPCS coding, clinical guidelines, or proof that payer policy criteria were met. Outcomes are not guaranteed and depend on payer-specific review.
What documentation strengthens a CARC 55 appeal?
Clinical literature, treatment guidelines, FDA approval or clearance records, prior authorization confirmation, and detailed provider notes demonstrating medical necessity typically support this type of appeal.
Should I resubmit instead of appealing?
If the issue is a coding error or missing information unrelated to the experimental classification, correcting and resubmitting the claim may be more appropriate than an appeal.
More free billing tools: all appeal letters · denial codes · NCCI edits · Medicare fees
This template is for informational purposes only and does not constitute legal, billing, or medical advice. It is a general framework to be customized with accurate, case-specific information. Appeals are not guaranteed to result in payment or reversal of a denial; outcomes depend on payer policies and the specifics of each claim.
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