Insurance Appeal Letter Templates: 5 Fill-in-the-Blank Scripts by Denial Type

A well-written insurance appeal letter directly rebuts the insurer's stated reason using their own policy language, clinical guidelines, and applicable federal or state law. Generic letters lose. Specific, documented letters win. Here are five templates — one for each major denial type — that you can fill in and send.

Common Denial Reasons and the Right Template

Before selecting a template, identify your denial type from the EOB and denial letter:

• Denial code 50 / N379 — Not medically necessary → Template 1
• Denial citing "investigational" or "experimental" → Template 2
• Denial for out-of-network provider → Template 3
• Prior Authorization Denied: How to Appeal" class="auto-link">Prior authorization denied or not obtained → Template 4
• Mental health or substance use treatment denied → Template 5

Documentation Checklist (All Types)

Before completing any template, gather:

• Denial letter with specific reason code and policy citation
• Explanation of Benefits (EOB)
• Full policy documents / Summary Plan Description
• Physician letter of medical necessity
• Medical records supporting the specific denial type
• Insurer's clinical policy bulletin (CPB) — request in writing
• Clinical guidelines from relevant medical associations

Template 1: Medical Necessity Denial

Use this when your insurer says the treatment was "not medically necessary."

[Your Name]
[Address]
[Date]

[Insurance Company Name]
Appeals Department
[Address]

RE: Appeal of Denial — Claim #[CLAIM NUMBER]
Member ID: [MEMBER ID] | Date of Service: [DATE] | Provider: [PROVIDER NAME]
Service Denied: [PROCEDURE/TREATMENT + CPT CODE]

Dear Appeals Reviewer:

I am writing to appeal the denial of [treatment/procedure] for the above-referenced
claim. The denial states that the service was not medically necessary. I respectfully
disagree and submit the following in support of coverage.

My treating physician, [DR. NAME], [SPECIALTY], has diagnosed me with [DIAGNOSIS +
ICD-10 CODE] and recommended [TREATMENT] as the appropriate course of care. This
determination is supported by [CLINICAL GUIDELINE — e.g., "the American Heart
Association 2023 Guidelines, which recommend [TREATMENT] for patients with [CRITERIA],
which I meet as documented in the attached records"].

I have previously attempted the following treatments without adequate response:
[LIST PRIOR TREATMENTS, DATES, AND OUTCOMES]

Per [YOUR PLAN NAME] Summary Plan Description, Section [X], coverage is provided for
services "medically necessary as determined by standard clinical criteria." The attached
Letter of Medical Necessity from Dr. [NAME] documents that [TREATMENT] meets this
standard for my clinical situation.

I request that you reverse this denial and approve coverage for [TREATMENT].

Enclosed: Denial letter, EOB, Letter of Medical Necessity, medical records, guidelines

Sincerely,
[Your Name] | [Phone] | [Email]

Template 2: Experimental or Investigational Treatment Denial

Use this when the insurer classifies your treatment as experimental or unproven.

RE: Appeal of Denial — Experimental/Investigational Classification
Claim #[CLAIM NUMBER] | Member ID: [MEMBER ID]

Dear Appeals Reviewer:

I am appealing [INSURER]'s determination that [TREATMENT] is experimental or
investigational for [DIAGNOSIS]. This classification is not supported by current
medical evidence or major clinical guideline bodies.

[TREATMENT] is:
- Approved by the FDA for [INDICATION] as of [DATE]
- Recommended in [GUIDELINE NAME + YEAR] for patients with [CRITERIA]
- Covered by [MEDICARE/MEDICAID or a named competing insurer] for this indication

Published peer-reviewed evidence demonstrates established clinical benefit, including:
- [STUDY 1: Authors, Journal, Year — Key Finding]
- [STUDY 2: Authors, Journal, Year — Key Finding]

Under the ACA and [YOUR STATE] insurance law, insurers are prohibited from classifying
treatments as experimental when they are supported by peer-reviewed literature and
recommended by recognized clinical authorities. [TREATMENT] meets both standards.

I request a full reversal of this denial. My physician Dr. [NAME] is available for a
peer-to-peer review at [PHONE NUMBER].

Enclosed: Denial letter, FDA approval document, clinical guidelines, published studies,
physician letter

Sincerely,
[Your Name]

Template 3: Out-of-Network Denial

Choose the paragraph that matches your situation.

RE: Appeal of Denial — Out-of-Network Services
Claim #[CLAIM NUMBER] | Member ID: [MEMBER ID]

Dear Appeals Reviewer:

I am appealing the denial/reduced payment for services rendered by [PROVIDER NAME],
categorized as out-of-network, on [DATE OF SERVICE].

[USE ONE OF THE FOLLOWING — DELETE THE OTHERS]

EMERGENCY CARE: These services were rendered in an emergency situation. Under the
No Surprises Act (effective January 1, 2022), out-of-network emergency care must be
covered at in-network cost-sharing levels. The emergency circumstances are documented
in the attached records from [FACILITY NAME].

NO IN-NETWORK ALTERNATIVE: No in-network provider with the necessary specialty
([SPECIALTY]) was available within a reasonable distance at the time of service.
[PROVIDER NAME] was the nearest qualified specialist who could provide timely care.
Network adequacy standards require access to this specialty; your network failed to
meet this standard.

CONTINUITY OF CARE: I had an established treatment relationship with [PROVIDER] prior
to [THE DATE THEY LEFT YOUR NETWORK / MY PLAN ENROLLMENT DATE]. Under [YOUR STATE]'s
continuity of care law [or ACA transition provisions], I am entitled to continue care
with this provider at in-network cost-sharing during an active course of treatment.

I request that this claim be reprocessed at in-network benefit levels.

Enclosed: Denial letter, emergency records or network search documentation, continuity
of care documentation as applicable

Sincerely,
[Your Name]

Template 4: Prior Authorization Denial

Use this to appeal a prior authorization denial before or after the service.

RE: Appeal of Prior Authorization Denial
PA Reference #: [PA NUMBER] | Member ID: [MEMBER ID]

Dear Appeals Reviewer:

I am appealing the denial of prior authorization for [TREATMENT/PROCEDURE] for my
diagnosis of [DIAGNOSIS + ICD-10 CODE]. The denial states [EXACT DENIAL REASON].

1. MEDICAL NECESSITY IS DOCUMENTED
[TREATMENT] is medically necessary as documented in the attached Letter of Medical
Necessity from Dr. [NAME]. My diagnosis of [DIAGNOSIS] requires this specific treatment
because [CLINICAL REASON FROM PHYSICIAN LETTER].

2. YOUR PLAN CRITERIA ARE MET
[INSURER]'s prior authorization criteria for [TREATMENT] require [LIST EACH CRITERION].
I meet all applicable criteria:
- [Criterion 1]: [How you meet it — with supporting record citation]
- [Criterion 2]: [How you meet it]
- [Criterion 3]: [How you meet it]

3. REQUIRED STEP THERAPY COMPLETED [DELETE IF NOT APPLICABLE]
I have completed required step therapy, having tried [TREATMENT A] from [DATE] to
[DATE] with inadequate response ([OUTCOME]), and [TREATMENT B] from [DATE] to [DATE]
with inadequate response ([OUTCOME]).

I request immediate approval of this prior authorization. Dr. [NAME] is available for
an expedited peer-to-peer review at [PHONE NUMBER].

[IF URGENT — ADD THIS:] This request is medically urgent. Delay poses risk of
[SPECIFIC HARM] as documented in the attached clinical letter. I request an expedited
decision within 72 hours as required by federal regulation.

Enclosed: Denial letter, Letter of Medical Necessity, medical records, step therapy
documentation

Sincerely,
[Your Name]

Template 5: Mental Health Parity Violation

Use this when mental health or substance use disorder treatment is denied more restrictively than equivalent medical care.

RE: Appeal of Denial — Mental Health Parity Act Violation
Claim #[CLAIM NUMBER] | Member ID: [MEMBER ID]

Dear Appeals Reviewer:

I am appealing the denial of [MENTAL HEALTH/SUD TREATMENT] and asserting that this
denial violates the Mental Health Parity and Addiction Equity Act of 2008 (MHPAEA)
and the Consolidated Appropriations Act of 2021 (CAA).

The MHPAEA requires that treatment limitations applied to mental health and substance
use disorder benefits be no more restrictive than those applied to medical/surgical
benefits in the same classification.

[INSURER] has denied [TREATMENT] on the grounds of [STATED REASON]. However, analogous
medical/surgical treatments — such as [COMPARABLE MEDICAL TREATMENT, e.g., "inpatient
rehabilitation after cardiac surgery"] — are covered under my plan without this
restriction.

I request that [INSURER]:
1. Provide in writing the specific nonquantitative treatment limitation (NQTL) applied
   to this denial
2. Provide the comparative analysis required by the CAA demonstrating parity between
   mental health and medical/surgical benefits
3. Reverse this denial and approve coverage for [TREATMENT]

If [INSURER] cannot demonstrate parity compliance, I will file complaints with the
[YOUR STATE] Department of Insurance and the U.S. Department of Labor Employee Benefits
Security Administration (EBSA).

Enclosed: Denial letter, physician letter, documentation of comparable medical/surgical
coverage under this plan

Sincerely,
[Your Name]

Universal Best Practices

Before sending any appeal letter:

• Send by certified mail (return receipt) AND through the insurer's online portal — create two proof trails
• Include your member ID, claim number, and date of service on every page
• Number all attachments and reference them in your letter by number
• State exactly what outcome you are requesting — don't leave it ambiguous
• Keep your own complete copy of everything submitted
• Note the appeal deadline and insurer's required response deadline

Fight Back With ClaimBack

These templates give you a strong starting structure. ClaimBack customizes the content for your specific denial, insurer, state laws, and clinical situation — inserting the right guideline citations, legal references, and medical evidence framework automatically based on your information. ClaimBack generates a professional appeal letter in 3 minutes.

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Related Reading

• How to Write an Insurance Appeal Letter
• What Is Medical Necessity?
• Internal vs External Insurance Appeal