Medicare Advantage EOB Shows a Denial You Don't Recognize

What This Means

Your Medicare Advantage plan received a claim from a provider — likely a surgeon, hospital, or specialist — and refused to pay part or all of it. Your Explanation of Benefits (EOB), the summary your plan sends after processing a claim, shows that denial as a line item. This can be alarming, especially after a major procedure, but an EOB denial is not a bill. It is the plan’s record of what it decided to cover and what it did not.

Why This Happens

• Prior authorization was missing or expired. Many Medicare Advantage plans require advance approval before surgery or certain procedures. If authorization was not obtained, or lapsed before the claim was submitted, the claim may be denied automatically.
• A provider was out-of-network. During a complex procedure, an assistant surgeon, anesthesiologist, or pathologist may have been involved without anyone checking their network status. Even one out-of-network provider can result in a denied line on your EOB.
• The plan’s coding didn’t match the provider’s coding. Claims are submitted using standardized billing codes. A mismatch between what the provider submitted and what the plan expected for your diagnosis can trigger a denial.
• The plan determined the service wasn’t medically necessary. Some procedures — even routine ones — get flagged for medical necessity review. The plan may have denied a specific service within a larger claim on those grounds.
• The claim arrived after the filing deadline. Plans have time limits for how long after a service a claim can be submitted. A late submission from a provider can result in a denial that looks confusing on your EOB.

Should You Appeal?

What To Do Next

1. Find the specific denial reason on your EOB. Look for a remark code or short explanation next to the denied line. This tells you whether the denial was about authorization, medical necessity, network status, or something else — and that determines your next step.
2. Call your Medicare Advantage plan. Use the member services number on the back of your insurance card. Ask them to explain the denial reason in plain language and confirm whether your provider can submit additional documentation to resolve it without a formal appeal.
3. Contact your provider’s billing office. They may already know about the denial and have started correcting it. Coding errors and missing authorization paperwork are often handled directly between the provider and the plan.
4. File a formal appeal if the denial stands. You typically have 65 days from the date on your denial notice to file a plan-level reconsideration — a formal request asking the plan to take another look. Your denial notice will include specific instructions.
5. Gather supporting documents before you appeal. Your EOB, the original denial notice, any prior authorization records, and a letter from your doctor explaining why the service was medically necessary are the core pieces of a strong appeal.
6. If you’d like help reviewing your EOB or understanding what was denied, contact your State Health Insurance Assistance Program (SHIP). SHIP counselors give free, unbiased Medicare help. Find yours at shiphelp.org or call 1-800-MEDICARE (1-800-633-4227).

Sources

• Medicare.gov — Appeals in a Medicare health plan (Medicare Advantage) — the 65-day plan-level reconsideration deadline and appeal levels
• Medicare.gov — How to file a complaint or appeal
• HHS OIG — Some Medicare Advantage Organization Denials Raise Concerns (OEI-09-18-00260, 2022)
• KFF — An Overview of Medicare

Frequently Asked Questions