Insurance Denial Appeal Letter Template

Every denied line carries a group code and a claim adjustment reason code (CARC), and often a remittance advice remark code (RARC). X12, which publishes the code lists, says reason codes describe why a claim or service line was paid differently than it was billed². The group code generally assigns responsibility: CO is contractual obligation and PR is patient responsibility.

Remark codes provide additional explanation for an adjustment already described by a Claim Adjustment Reason Code³, and that detail usually tells you what to fix. For CARC 16, the general billing-error code, X12's usage note says at least one remark code must be provided². So when a CO-16 arrives without one, ask the payer what is missing.

An appeal disputes the payer's decision. A corrected claim fixes an error in what you sent, such as a wrong code or a missing modifier. Sometimes the payer decides for you: remark code MA130 says no appeal rights are afforded because the claim is unprocessable³ and asks for a new claim.

CMS says Medicare contractors do not process claim corrections involving minor errors and omissions through the appeals process⁴. Those go through a reopening instead. Give every denied line one of four routes, and note why:

• Corrected claim: your submission had a fixable error.
• Appeal: the claim was right and the decision was wrong.
• Ask the payer: the codes don't say what to fix.
• Write off: the denial is correct, or not worth the work.

Date the deadline before you draft, and note its source. What starts the count matters as much as the number of days, so read the appeal rights on the denial notice first.

For Original Medicare, CMS allows 120 days from the date of receipt of the initial claim determination⁴. Employer group health plans covered by ERISA must allow at least 180 days following receipt of a notification of an adverse benefit determination⁵. The same rule lets an authorized representative appeal for the patient, under the plan's own procedure for naming one, so get that paperwork signed early.

Number every exhibit. Always include the remittance or denial notice and the claim exactly as sent, then add what the denial type needs:

• Authorization: the approval, with its number, dates, codes, provider and site.
• Medical necessity: the payer's policy, its criteria and dated notes that meet each one.
• Timely filing: proof of the original submission date.

Find the exact policy before arguing medical necessity. Remark code N115 says the decision was based on a Local Coverage Determination³, a Medicare policy you can read in CMS's coverage database. An ERISA group health plan's denial notice must include the specific rule, guideline, protocol, or other similar criterion⁵ it relied on, or say a copy is free on request.

Keep it short and in a fixed order, so a busy reviewer finds the disputed line at once. Use the payer's own form if it has one. Original Medicare accepts form CMS-20027 or a letter. The letter must include the beneficiary's name, Medicare number, the services and dates of service, the name of the party and why you disagree⁴.

1. 1

   Identify the claim

   Patient, member ID, claim number, dates of service, billed and denied amounts, rendering NPI and appeal level.

2. 2

   Quote the determination

   Give the group, reason and remark codes with their published descriptions.

3. 3

   Ask for one thing

   One sentence, before the argument: reprocess the line and pay it at the contracted rate.

4. 4

   Prove each point

   Tie each fact to a numbered, dated exhibit, and answer the policy's criteria in order.

Log each appeal the day it goes out: deadline, date sent, confirmation number and reply due date. Chase anything overdue, and keep proof of the filing date.

An upheld denial starts a new clock for the next level. Original Medicare has five levels. CMS's appeals booklet for providers gives you up to 180 days after you get the Medicare Redetermination Notice⁶ to request the second, an independent reconsideration. Send all your evidence then, because later levels consider new evidence only if you show good cause.

Few denials are ever appealed, yet many appeals succeed. The HHS Office of Inspector General found that patients and providers appealed only 1% of Medicare Advantage denials in 2014 to 2016. When they did, plans overturned 75% of their own denials⁷. Results vary by market: in 2024, insurers on HealthCare.gov upheld 66% of the denials consumers appealed¹.

For prior authorization denials, the prior authorization appeal letter answers the plan's stated reason point by point, and the medical necessity letter lines up each coverage criterion with the record. The prior authorization template tracks what each payer asks for before you request approval. The template on this page keeps the register, deadlines, payer rules and letter together, and River can fill the register from your remittance.