Health Insurance Claims

How to Appeal a Health Insurance Claim Denial in the U.S.: Step-by-Step Guide

A significant share of in-network health insurance claims in the United States are initially denied. Many denials are later reversed through internal appeals or external review, particularly under Affordable Care Act (ACA) plans, Medicare, Medicaid, and most employer-sponsored coverage. Common reasons include coding or billing errors, determinations that a service is not medically necessary, missing prior authorization, benefit exclusions, or administrative issues. This guide outlines the standard appeal process available to most insured individuals.

Common Reasons for Claim Denials

Insurers may deny claims for:

• Incorrect or incomplete coding (CPT, HCPCS, or ICD-10 codes)
• Lack of demonstrated medical necessity
• Failure to obtain required prior authorization
• Services excluded by the policy or exceeding benefit limits
• Out-of-network status when the plan requires in-network care
• Incomplete or untimely documentation

Patients receive notice of the denial through an Explanation of Benefits (EOB) or formal denial letter that states the reason and outlines appeal rights and deadlines.

Step 1: Obtain and Review the Explanation of Benefits (EOB)

Act promptly. Appeal deadlines typically range from 30 to 180 days from the date of the denial notice, depending on the plan type.

• Request the complete EOB and any supporting documentation from the insurer’s member portal or by phone.
• Note the claim number, denial reason or code, denied amount, and stated appeal deadline.
• Compare the EOB with the provider’s itemized bill and clinical records.

If the denial appears to result from a simple billing or coding error, contact the provider’s billing office first; many such issues can be corrected and resubmitted without a formal appeal.

Step 2: Gather Supporting Documentation

Successful appeals rest on clear evidence. Assemble:

• Relevant medical records (progress notes, diagnostic results, operative reports)
• A letter of medical necessity from the treating physician explaining why the service was required and why alternatives were not appropriate
• Copies of the policy provisions or Summary of Benefits that appear to cover the service
• Prior authorization requests and responses, if applicable
• Itemized bills and any correspondence with the insurer

For ACA plans, essential health benefits and prohibitions on lifetime or annual dollar limits may be relevant. Reference the specific plan documents.

Step 3: Attempt Informal Resolution

Before filing a formal appeal:

• Contact the provider’s billing department to confirm coding accuracy and request resubmission if an error is identified.
• Call the insurer’s member services line (number on the insurance card) and request a peer-to-peer review between the treating physician and the insurer’s medical director. Document the date, representative name, and reference number of every call.

Informal correction resolves a portion of denials without further process.

Step 4: File a Level 1 Internal Appeal

Submit a written appeal to the address or portal designated by the insurer within the stated deadline. Send by certified mail with return receipt or through the insurer’s secure electronic system and retain proof of submission.

A concise appeal letter should include:

• Member name, policy number, and claim number
• Clear statement that the letter is a formal appeal of the denial
• Brief description of the denied service and the stated reason for denial
• Clinical and policy-based arguments supporting coverage
• List of attached exhibits
• Specific request for reversal and payment

Keep a complete copy of the submission package.

Step 5: Track the Internal Appeal and Proceed to Level 2 if Necessary

Under ACA rules, insurers generally must respond to a standard internal appeal within 30 days (or 72 hours for urgent cases). Employer plans subject to ERISA follow similar timelines with some variation.

If the Level 1 appeal is denied, most plans provide a second internal level. Submit any additional evidence or clarification at that stage and continue to document all communications.

Step 6: External Review

If internal appeals are exhausted, eligible plans (including most ACA Marketplace, individual, and many group plans) offer an independent external review at no cost to the patient. The external reviewer is not employed by the insurer.

• The insurer or the state insurance department provides instructions for requesting external review.
• Deadlines and procedures vary by state and plan type; many states administer the process through their Department of Insurance or an independent review organization.
• Urgent cases often receive expedited review (typically within 72 hours).

Medicare Advantage and certain other federal programs have separate, often faster, appeal pathways that may culminate in an Administrative Law Judge hearing.

Plan Type	Typical External Review Path	Notes
ACA Marketplace / Individual	State external review or federal process	Free
Fully insured group	State external review in most cases	Free
Self-funded ERISA group	Limited external review; court remains option	Varies
Medicare Advantage	Medicare appeal process (including ALJ)	Specific timelines

Additional Options

• File a complaint with the state Department of Insurance.
• For ERISA plans, contact the U.S. Department of Labor.
• Patient advocacy organizations can provide free or low-cost assistance with documentation and process navigation.

Practical Tips

• Calendar all deadlines immediately upon receiving the denial.
• Maintain organized records of every document, call, and submission.
• Request peer-to-peer review early when medical necessity is disputed.
• For urgent or ongoing care, explicitly request expedited review and document the clinical urgency.
• Confirm whether the plan is fully insured or self-funded, as this determines available external remedies.

Claim denials are common, yet a structured, well-documented appeal frequently results in reversal. Begin with the EOB and clinical records, follow the plan’s stated process and deadlines, and escalate systematically through internal and external levels as needed. Official resources include the insurer’s member materials, Healthcare.gov (for Marketplace plans), the state Department of Insurance, and Medicare.gov for Medicare-related appeals.

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