Guide
How to Appeal a Health Insurance Denial
To appeal a health insurance denial, you have the right to a full and fair review under federal law. For employer-sponsored plans, ERISA § 503 and 29 CFR § 2560.503-1 govern the process. For ACA marketplace plans, PHS Act § 2719 and 45 CFR § 147.136 apply. You typically have 180 days from the denial date to file.
Most people never appeal. Insurers count on it. This guide explains exactly what to do.
Step 1: Find your denial code
Your first stop is the Explanation of Benefits (EOB) your insurer sent after the claim. Look for the CARC code — a two- or three-digit number that tells you the exact denial reason.
Common examples: CARC 50 (medical necessity), CARC 96 (non-covered charge), CARC 97 (procedure unbundling), CARC 29 (time limit expired).
The CARC code determines which federal regulations apply and whether you are the right person to appeal. Some codes (CO-group codes) indicate a provider billing adjustment — the patient owes nothing and no appeal is needed. PR-group codes indicate patient responsibility and are the ones to appeal.
Browse the full denial code directory to look up your code and confirm it is patient-appealable.
Step 2: Identify your plan type
Two major federal frameworks govern health insurance appeals:
- –ERISA plans — employer-sponsored plans at private companies. Governed by ERISA § 503 and 29 CFR § 2560.503-1. The most common type.
- –ACA plans — marketplace (exchange) plans and most individual plans. Governed by PHS Act § 2719 and 45 CFR § 147.136.
Your insurance card, your employer's benefits documents, or your denial letter will indicate the plan type. If you obtained coverage through healthcare.gov, you are on an ACA plan. If your employer provides it and your employer is a private company, you are almost certainly on an ERISA plan.
The distinction matters because response deadlines, external review rights, and the specific regulatory language you cite in your appeal letter differ between the two.
Step 3: Write your appeal letter
An effective insurance appeal letter does three things:
- –States the specific denial reason (your CARC code) and why it was incorrectly applied
- –Cites the federal regulations that govern your plan's appeal obligations
- –Requests a specific remedy (overturn the denial and process the claim)
Regulatory citations matter. Generic appeal letters — "I disagree with this denial" — are routinely ignored. Letters that cite specific provisions of 29 CFR § 2560.503-1 or 45 CFR § 147.136 land on the desks of insurers' legal and compliance teams, who are obligated to respond specifically to those citations.
Rebuttal reads your denial letter, identifies the exact federal regulations that apply to your CARC code and plan type, and drafts the complete appeal letter for $9.99. Draft your appeal letter now.
Step 4: Gather supporting documents
The appeal letter establishes the legal basis. Supporting documents establish the facts. Gather as many of the following as apply to your denial:
- –Explanation of Benefits (EOB) — from your insurer's member portal
- –Summary of Benefits and Coverage (SBC) — from your employer's HR department or insurer's website
- –Doctor's letter of medical necessity — request directly from your physician, ask specifically for "a letter of medical necessity for insurance appeal"
- –Clinical notes and records — the visit notes supporting why the service was needed
- –Prior authorization record — confirmation number and correspondence if authorization was obtained
- –Itemized bill — line-by-line breakdown with procedure codes from your provider's billing department
Not all of these apply to every denial. Your denial's CARC code will indicate which type of evidence is most relevant.
Step 5: Submit and track
Where to send it: Your appeal mailing address is in your denial letter under "How to appeal" or "Your appeal rights." If you cannot find it, call the member services number on your insurance card and ask specifically: "What is the mailing address for formal written appeals?"
How to send it: Certified mail with return receipt creates a legal paper trail and proves delivery. Some insurers offer an online portal — take a screenshot confirming submission before closing the page.
Track the date: Your appeal deadline runs from the denial date on your EOB, not from when you received it. Keep a copy of everything you send.
Step 6: What insurers must do next
Federal law sets minimum response timelines that your insurer must follow:
| Claim type | Required response time |
|---|---|
| Non-urgent claims | 60 days |
| Urgent or pre-service claims | 72 hours |
| Concurrent care decisions | 24 hours |
The insurer must provide a written decision that specifically addresses your arguments and cites the plan provisions and clinical criteria they relied on. A response that simply restates "denial upheld" without addressing your arguments may itself be a regulatory violation.
Step 7: If your appeal is denied
You have additional options:
External review (ACA plans): Under 45 CFR § 147.136, you have the right to independent external review. The reviewer's decision is binding on your insurer — they cannot simply override it.
External review (ERISA plans): Rights depend on your state and whether your plan is self-funded. Fully insured employer plans are subject to state external review mandates. Self-funded plans may be exempt.
Deemed exhaustion: Under 29 CFR § 2560.503-1(l), if your plan fails to follow its own appeal procedures — missing deadlines, failing to send required notices — your claim is deemed exhausted. You can immediately proceed to external review or litigation without completing the internal process.
State insurance commissioner: File a complaint if you believe the insurer violated state or federal law. Most states have an online portal.
Department of Labor (ERISA plans): File a complaint with the Employee Benefits Security Administration at dol.gov/agencies/ebsa.
Frequently asked questions
How long do I have to appeal an insurance denial?
Most employer-sponsored (ERISA) plans give you 180 days from the denial date. ACA marketplace plans also provide at least 180 days, though your denial letter may specify a shorter window. The deadline runs from the denial date on your EOB — not when you received it.
Can I appeal any insurance denial?
You can appeal most clinical denials — medical necessity, prior authorization, experimental treatment, coding disputes. Denials coded as provider billing adjustments (CO-group CARC codes) are typically between your provider and the insurer; the patient owes nothing and a patient appeal is not the right path.
What happens after I file an appeal?
Your insurer must respond in writing within the federal timeframes above. Their response must specifically address your arguments and cite the plan provisions they relied on. A vague or non-responsive reply may be a regulatory violation you can flag in a follow-up or escalation.
What is external review?
External review is independent review by a third-party organization not employed by your insurer. For ACA plans, the result is binding on the insurer. For ERISA plans, availability depends on your state and plan type. External review is typically available after an internal appeal is denied.
See also: ERISA appeal rights explained · Insurance appeal deadlines · Denial code directory · Submission guide
Not legal or medical advice. Rebuttal is a document drafting tool, not a law firm. Review your letter before submitting and consult a licensed professional for legal questions specific to your plan.