November 2026

Medical Billing Appeals: What to Do After a Denial

Most denials are not final. The denial reason on the EOB is usually the part that tells you whether the bill can still be fixed. Here’s how the appeal process works in plain English.

The Denial Is Not Always the End

When an insurer denies a claim, the Explanation of Benefits (EOB) shows a denial reason code. That code is the starting point. Many denials are overturned on appeal because the original claim was missing information, not because the service was truly non-covered.

Common reasons include medical necessity not met, coding issues, missing prior authorization, timely filing problems, or a service the plan says is not covered. The first step is reading the exact reason on the EOB instead of only looking at the patient responsibility amount.

Internal Appeal First

Most plans require an internal appeal before anything else. This is a formal request asking the insurer to review the denial again. Deadlines are usually 180 days from the denial notice, but they vary by plan and state. Missing the deadline often ends the right to appeal.

The appeal should include:

• The denial notice and EOB
• A short letter explaining why the claim should be paid
• Supporting records (chart notes, medical necessity letter, prior authorization if it existed)
• Any coding rationale if the issue was a code or modifier

External Review After Internal Appeal

If the internal appeal is denied, many plans allow an external review by an independent review organization. Under the Affordable Care Act, this is available for most commercial plans for medical necessity and similar denials. The reviewer is not the insurer.

External review has its own deadline, usually 4 months after the final internal denial. The decision is often binding on the insurer.

What Improves the Odds

Clean documentation matters more than a long letter. A focused medical necessity statement from the treating clinician, clear chart notes, and a plain explanation of why the denial reason does not apply tend to work better than generic appeals.

Patients can file appeals themselves. Providers often handle them because they already have the records and coding details. Either way, the process starts with the denial reason on the EOB.

Practical Next Steps

1. Read the exact denial reason code on the EOB.
2. Note the deadline for appeal.
3. Gather the supporting documents listed above.
4. Send the internal appeal and keep proof of delivery.
5. If denied again, check whether external review is available.

BillClear is built to help surface the denial reason and related line items in plain English so the next step is clearer. The appeal itself is still a formal process with deadlines.

This article is for informational purposes only and is not medical or legal advice. Deadlines and rules vary by plan and state.