How to Appeal an Insurance Denial

To appeal an insurance denial, read the denial letter for the exact reason and the appeal instructions, gather your EOB, medical records, and a letter from your doctor on medical necessity, then send a written appeal by certified mail that names the claim number and date of service, answers the denial reason with evidence, points to the plan's coverage terms, and asks for a written decision. Most plans give you 180 days to appeal; on most employer plans the plan has 60 days to decide an appeal for care you already received. If the internal appeal is denied, you have the right to an external review by an independent third party, and you can complain to your state insurance commissioner.

You went to the doctor. You had a procedure. Your insurance was supposed to cover it. Then the letter arrives: claim denied.

It feels final. It's designed to feel final. But here's the truth the insurance industry doesn't want you to know: denials are not the end of the conversation. They're the beginning of a process — and the process is written down.

Here's what insurers count on: most denials are never appealed. In a KFF analysis of CMS data (2023), marketplace insurers denied about 1 in 5 in-network claims and consumers appealed under 1% of them. Insurance companies profit from the gap between what people are owed and what they're willing to fight for.

Don't be in the silent majority.

Why Claims Get Denied

Understanding why your claim was denied is the first step to overturning it. The most common reasons include:

• Prior authorization not obtained — your provider didn't get pre-approval
• Out-of-network provider — you saw a doctor outside your plan's network
• Medical necessity — the insurer says the treatment wasn't necessary
• Coding errors — the wrong CPT or diagnosis code was submitted
• Missing information — the claim was incomplete or had errors
• Timely filing — the claim was submitted past the deadline

Look at your denial letter closely. It must tell you why the claim was denied and how to appeal. If it doesn't, that itself may be a violation.

The Appeals Process: Step by Step

Step 1: Read the Denial Letter Carefully

Your denial letter contains the specific reason for denial, the plan provisions they're citing, and instructions for filing an appeal. Read every word. The reason matters because your appeal needs to address it directly.

Step 2: Gather Your Documentation

Build your case. Collect:

• The denial letter
• Your EOB (Explanation of Benefits)
• Medical records related to the treatment
• A letter from your doctor explaining why the treatment was medically necessary
• Any prior authorization records
• Your insurance plan's Summary of Benefits

Your doctor's letter is often the most important piece. Insurers deny claims for lack of medical necessity — your doctor can counter that with clinical evidence.

Step 3: The Appeal Letter

An appeal has to do specific things: name the claim number and date of service, state that you are appealing, answer the exact denial reason with evidence, point to the plan's coverage terms, enclose the supporting documents, and ask for a written decision within the plan's deadline. Factual, specific, and firm. Not a plea — an assertion of rights.

BillFighter's Insurance Appeal letter does exactly this. It references the denial reason and code from your EOB or denial letter, states why the care was medically necessary, asks that the denial be overturned and the claim reprocessed, notes your right to external review, and asks for a written determination. Upload the denial letter and the EOB and it is prepared under your name.

Step 4: Send It and Track It

The appeal goes to the address listed in the denial letter by certified mail, so there is a delivery record. You read it, sign it, and mail it yourself or have BillFighter send it. Keep copies of everything, and note the date: the plan has a deadline to decide (on most employer plans, 60 days for care you already received, and much less for urgent care). If the deadline passes with no decision, BillFighter's Follow-Up Letter demands the written determination.

Step 5: Escalate If Needed

If your internal appeal is denied, you have the right to an external review — an independent third party reviews your case. Under the ACA, nearly all marketplace and employer plans must offer external review.

You can also file a complaint with your state insurance commissioner and, for some plans, the Department of Health and Human Services. Regulators have real teeth, and insurers take their inquiries seriously. When an insurer ignores a certified appeal, BillFighter's Insurance Commissioner Complaint letter lays out the record for the commissioner: the appeal, the delivery date, the silence.

Common Mistakes to Avoid

• Missing the deadline — most plans give you 180 days to appeal, but don't wait
• Being vague — your appeal must address the specific denial reason
• Not including your doctor — a physician's support letter answers the medical-necessity reason directly
• Giving up after the first denial — there are multiple levels of appeal for a reason

What BillFighter Does Here

The paperwork is the exhausting part. BillFighter reads the denial and the EOB, then prepares the Insurance Appeal under your name, addressed to the denial reason on the page. If the insurer goes silent, the Follow-Up Letter demands the decision; if that goes unanswered too, the Insurance Commissioner Complaint puts the record in front of the regulator. You read every word, decide whether to send it, and sign it. Mail it yourself, or have BillFighter send it by certified mail. BillFighter does not talk to the insurer and does not negotiate for you. It hands you the paperwork.

Your claim was denied. That doesn't mean it's over. Check my bill, free →