What should I include in an insurance appeal letter?

An insurance appeal letter must include: (1) Patient name and insurance member ID; (2) Claim number and date of service; (3) The denial code and reason from the EOB; (4) A clear clinical argument for why the denial should be overturned; (5) References to the payer's clinical criteria (e.g., InterQual® for UHC, MCG for Aetna); (6) Supporting documentation (physician notes, prior auth, lab results); (7) Evidence of failed conservative treatments if applicable; (8) Provider NPI and signature; (9) A list of all attachments. Generic letters without payer-specific criteria citations are significantly less effective — customizing your language to match the payer's own review criteria is the single highest-impact improvement you can make.

How do I use this insurance appeal letter template?

Replace every placeholder in brackets — [PATIENT NAME], [CLAIM NUMBER], [DENIAL CODE], etc. — with the actual values from your Explanation of Benefits (EOB). Then customize the clinical argument section (paragraph 3) to cite your patient's specific diagnosis, treatment history, and relevant clinical guidelines. Do not send the template verbatim — insurers recognize and deprioritize form letters. For a fully personalized letter generated in 60 seconds, use AppealFlow's AI generator instead.

What is the appeal deadline for my insurance company?

Appeal deadlines by payer: UnitedHealthcare — 65 calendar days (the shortest in the industry); Aetna — 180 days; Cigna — 180 days; Anthem/BCBS — 180 days (365 days in California); Medicare Part B — 120 days; Medicare Advantage — 60 days. Always verify the deadline from your specific denial notice — it is legally required to be disclosed. Missing the deadline typically results in permanent, unrecoverable revenue loss.

What is a CO-50 denial and how do I appeal it?

CO-50 means the service was denied as 'not medically necessary' according to the payer's clinical criteria. To appeal a CO-50: cite the payer's specific medical necessity criteria (InterQual® for UHC, MCG for Aetna/Cigna); document the patient's diagnosis, severity, and failed conservative treatments with dates and specifics; include relevant clinical guidelines (NCCN, ACR, specialty society standards); and request a peer-to-peer physician review simultaneously. CO-50 appeals with proper clinical documentation have overturn rates of 50–75%.

Can I appeal a denied claim more than once?

Yes. Most commercial health plans offer two levels of internal appeal. If both are denied, you have the right to an external independent review (required by the ACA for most commercial plans), where an accredited third party — not the insurer — makes the final decision. External review overturns 40–60% of internal appeal denials. For Medicare, the appeal ladder is: Redetermination → Reconsideration → Administrative Law Judge (ALJ) Hearing → Medicare Appeals Council → Federal District Court.

What is the difference between this template and AppealFlow's AI generator?

This template is a static starting point — you fill in the blanks and customize the clinical argument manually. AppealFlow's AI generator produces a fully personalized appeal letter in under 60 seconds: it incorporates your specific denial code, payer, diagnosis, and patient context; applies payer-specific criteria language (InterQual®, MCG, proprietary coverage policies); and structures the medical necessity argument based on patterns from thousands of successful appeals. The template works — but a personalized letter outperforms a form letter every time.

Free Insurance Appeal Letter Template for Denied Claims

More than 50% of denied healthcare claims are overturned on appeal — but only when the appeal letter is complete, specific, and tailored to the payer's clinical criteria. The template below gives you the correct structure. It won't write the clinical argument for you, but it ensures you don't miss a required element that would get your letter rejected or ignored on procedural grounds.

Before you use this template, pull the Explanation of Benefits (EOB) for the denied claim. You'll need the claim number, denial code, date of service, and the specific reason stated for the denial. Every field in the template is required — payers can and do reject appeals that are missing member IDs, provider NPIs, or denial codes.

If you want a personalized letter that incorporates payer-specific clinical criteria language and is ready to send in under 60 seconds, use AppealFlow's AI generator instead. The template below is a starting point — a personalized letter always outperforms a form letter.

Skip the template. Generate a fully personalized appeal letter in 60 seconds — payer-specific criteria, denial code targeted, ready to send.

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Free Insurance Appeal Letter Template

Copy this template and replace all [BRACKETED FIELDS] with your actual claim information. The clinical argument section (paragraphs 3 and 4) must be customized — do not send it with placeholder text.

Insurance Appeal Letter — Sample Template

[DATE] [INSURANCE COMPANY NAME] Appeals Department [PAYER ADDRESS] [CITY, STATE, ZIP] Re: Appeal of Claim Denial Patient Name: [PATIENT FULL NAME] Member ID: [INSURANCE MEMBER ID] Date of Birth: [PATIENT DATE OF BIRTH] Claim Number: [CLAIM NUMBER] Date of Service: [DATE OF SERVICE] Denial Code: [DENIAL CODE, e.g. CO-50] Provider Name: [PROVIDER/PRACTICE NAME] Provider NPI: [PROVIDER NPI] Dear Appeals Representative, I am writing to formally appeal the denial of the above-referenced claim. The claim was denied on [DATE OF DENIAL] with denial code [DENIAL CODE], citing [DENIAL REASON AS STATED ON EOB]. We respectfully disagree with this determination and request that the claim be reconsidered and approved. [PATIENT FIRST NAME] is a [AGE]-year-old patient with a documented diagnosis of [PRIMARY DIAGNOSIS WITH ICD-10 CODE]. The denied service — [SERVICE/PROCEDURE NAME WITH CPT CODE] — is medically necessary for this patient given [BRIEF CLINICAL RATIONALE: diagnosis severity, relevant history, failed prior treatments]. [CUSTOMIZE THIS PARAGRAPH: Cite the payer's specific medical necessity criteria. For UnitedHealthcare, reference InterQual® criteria. For Aetna or Cigna, reference MCG (Milliman Care Guidelines). Quote the relevant criterion and explain how your patient meets it. Include failed conservative treatments with dates, drug names, doses, and documented responses. This paragraph is the most important part of the letter — generic language here will result in a second denial.] Supporting documentation enclosed with this appeal includes: [LIST ALL ATTACHMENTS: physician notes, prior authorization, lab results, referral letters, treatment history, etc.] Based on the above clinical evidence and [PAYER NAME]'s own coverage criteria, we believe this claim meets the requirements for coverage and respectfully request that the denial be overturned. Please process this appeal within the timeframe required by [STATE] law and your plan's appeal procedures. If you require additional information, please contact our office at [PHONE NUMBER] or [EMAIL ADDRESS]. Respectfully, [PROVIDER SIGNATURE] [PROVIDER NAME, CREDENTIALS] [PRACTICE NAME] [PRACTICE ADDRESS] [PHONE / FAX] Enclosures: [LIST ATTACHED DOCUMENTS]

When to Use This Template

This template applies to most standard claim denials, but the clinical argument section must be tailored to the specific denial code. Here are the three most common denial scenarios and what the customization requires:

CO-50 — Not Medically Necessary

CO-50 is the most common denial code in healthcare billing, accounting for roughly 30% of all commercial denials. The insurer is saying the service doesn't meet its clinical necessity standards — not that it was uncovered or incorrectly coded. To appeal CO-50 effectively, your letter must cite the payer's own clinical criteria by name (InterQual®, MCG, or the payer's proprietary coverage policy), demonstrate that the patient meets those criteria, and document failed conservative alternatives with specifics. A peer-to-peer review request submitted alongside this letter improves overturn rates by an additional 15–25%.

CO-4 — Procedure Inconsistent with Modifier

CO-4 denials indicate a coding discrepancy — the modifier submitted doesn't match the procedure code, or the combination is flagged as incorrect. These are often correctable billing errors rather than clinical disputes. Before appealing, verify the modifier usage with your billing team. If the modifier was correct and the denial is a payer processing error, your appeal letter should include the original claim, a corrected claim if applicable, and documentation supporting the modifier's medical appropriateness (operative notes, anesthesia records, or a physician attestation).

CO-16 — Missing or Incomplete Information

CO-16 means the claim was rejected because required information was missing — no prior authorization number, missing diagnosis code, incomplete patient information, or absent documentation. These denials are typically straightforward: identify the missing element from the EOB remark codes, add it, and resubmit. For CO-16 appeals, attach the complete documentation and explicitly state in your letter which information was missing and that it is now included. Timely filing deadlines still apply even if the denial was administrative, so do not delay resubmission.

Key Elements Every Appeal Letter Needs

Before you submit, verify your letter includes all of the following. Appeals are rejected on procedural grounds more often than most billers realize — a missing NPI or claim number alone can cause a denial to be returned without review.

✓
Patient identification — Full legal name, date of birth, and insurance member ID exactly as they appear on the insurance card. Mismatches cause administrative rejections.
✓
Claim number and date of service — From the Explanation of Benefits (EOB), not estimated or approximate. The appeal must be matched to a specific claim on file.
✓
Denial code and stated reason — Quote the denial code exactly (CO-50, CO-4, etc.) and include the reason as written on the EOB. This ensures the appeal addresses the actual denial basis.
✓
Payer-specific criteria citation — Name the specific clinical criteria you're appealing under (InterQual® Level of Care, MCG, or the payer's published coverage policy). Generic "medically necessary" language without a criteria reference is the most common reason strong clinical appeals still fail.
✓
Clinical argument — A specific, evidence-based explanation of why the service meets the cited criteria. Include diagnosis with ICD-10, relevant history, and documentation of failed conservative treatments with dates and outcomes.
✓
Supporting documentation list — Enumerate every attachment: physician notes, prior authorizations, lab results, referral letters, operative reports, or treatment summaries. Payers are required to review what you submit — don't assume they'll request missing documents.
✓
Provider NPI and signature — Required on all appeals. Some payers will not process appeals without the ordering or rendering provider's signature and NPI, particularly for medical necessity denials.
✓
Submitted before the deadline — UnitedHealthcare's 65-day window is the shortest in the industry. Verify the deadline from the denial notice itself — it is legally required to appear there. Missing the deadline is typically unrecoverable.

Payer-Specific Tips and Deadlines

Each major payer has different appeal deadlines, submission methods, and clinical criteria preferences. Using the wrong criteria language for a given payer — e.g., citing MCG when appealing a UHC denial — signals to the reviewer that the letter is a form submission. Matching your language to the payer's own review tools is one of the highest-impact improvements you can make to a medical necessity appeal.

Payer	Appeal Deadline	Clinical Criteria	Key Tip
UnitedHealthcare	65 days	InterQual® Level of Care	Cite specific InterQual® criteria by name. UHC's medical directors respond well to peer-reviewed literature and failed conservative treatment documentation. Peer-to-peer rates: 70–85% overturn.
Aetna	180 days	MCG (Milliman Care Guidelines)	Reference MCG criteria by guideline number when available. Aetna accepts electronic appeals via Availity. Include clinical evidence alongside criteria citations — Aetna reviewers expect both.
Cigna	180 days	MCG + proprietary coverage policies	Check Cigna's online Coverage Policy Library for the specific denial before appealing — Cigna publishes its criteria publicly. Matching your argument to the exact policy language significantly improves success rates.
Anthem / BCBS	180 days (CA: 365d)	InterQual® or proprietary	Anthem criteria vary by state and plan type. Always pull the specific coverage policy for the denied service from Anthem's provider portal before writing the appeal. California members have extended protections under state law.
Medicare (Part B)	120 days	LCD / NCD (CMS guidelines)	Appeal Medicare denials using the Redetermination process (Level 1). Cite the relevant Local Coverage Determination (LCD) by number. Medicare requires specific documentation that the service meets the indications in the LCD — attach all supporting records.
Medicare Advantage	60 days	Plan-specific (varies by carrier)	Medicare Advantage plans use commercial criteria (InterQual®/MCG) despite being Medicare-funded. Check the specific plan's Evidence of Coverage document for criteria references. Deadline is 60 days from denial notice.

Payer-specific language built in automatically. AppealFlow incorporates the right criteria citations for every payer and denial code — no manual lookup required.

Generate a Personalized Appeal →

For a complete walkthrough of the full appeal process — from reading your EOB to submitting an external independent review — see the How to Appeal a Healthcare Insurance Denial guide. The guide covers the six-step process, CARC denial code reference table, overturn rate benchmarks by payer, and when to escalate to external review.