The short answer
An Explanation of Benefits is a notice from your plan, not a bill. If it shows a denial, your insurer must tell you in writing why. You then have 180 days from receiving that notice to file an internal appeal, and if the internal appeal fails you can take it to an independent external reviewer.
An EOB is a notice showing the costs of your care, not a demand for payment.
The insurer must notify you in writing and explain why a claim was denied.
You have 180 days from the denial notice to file an internal appeal.
Decisions are due within 15 days for prior authorization, 30 days for services already received, and 72 hours for urgent care cases.
Choose how you want to understand this
The full explanation.
First, breathe: this is a notice, not a bill.
The word "denied" on an Explanation of Benefits (EOB) sounds like a verdict. It is not one. CMS says an EOB is a notice from your health plan. It shows the costs of your care. It is not the bill your provider sends you for payment.
So do nothing financial first. Do not pay. Do not assume you owe the full amount. A denial at this stage is just the start of a process. Federal rules give you the right to run that process.
Denials get overturned. The people who appeal are the ones who find that out.
Read the reason, because everything hinges on it.
When an insurer refuses a claim, it must tell you why in writing. That written reason shapes your whole plan.
Some denials are simple mistakes. Maybe it was the wrong code, a missing referral, a name mismatch, or the wrong date on a bill. A phone call often fixes these. Your provider's billing office calls the plan, and no formal appeal is needed. Ask your clinic's billing staff to check the reason code first. They read these all day.
Other denials go deeper. The plan may say the service was not needed, was not covered, or needed approval it never got first. Those need a real appeal.
The internal appeal.
An internal appeal is your request. You are asking the insurance company to fully and fairly review its own choice. HealthCare.gov lists three steps. First, you or your provider file a claim. Next, the insurer denies it in writing and gives reasons. Then you formally push back on that denial with more proof.
To file, you should:
- Fill out any forms your insurer wants. Or write a letter with your name, claim number, and insurance ID number.
- Send in proof. A letter from your doctor and your medical records both work well.
- Call your state's Consumer Assistance Program if you want help filing.
You have 180 days — about six months — from the day you get the denial notice. Do not let that clock run out while you wait for a provider to fix things on their own. Filing your appeal does not stop a phone-call fix from happening at the same time.
How long the insurer gets.
Two different clocks run here, and they are easy to mix up.
The first is for the original claim decision. HealthCare.gov says the plan must tell you within 15 days if you are seeking prior authorization for a treatment. It is 30 days for medical services already received, and 72 hours for urgent care cases.
The second is for the appeal itself. The plan must decide within 30 days if the appeal is for a service you have not received yet. It has 60 days if the appeal is for a service you have already received.
If waiting the normal time could hurt your health, ask for a faster decision. A final answer on an expedited appeal must come at least within 4 business days after your request is received.
For someone in active cancer treatment, this matters a lot. If a denial is holding up planned treatment, say so clearly. Ask for the fast track. Do not just file quietly and wait.
If the internal appeal fails.
You still have options. HealthCare.gov says you can take the appeal to an outside reviewer. This means the insurance company no longer has the final word on your claim. Send your written request within four months of the final denial. You will find the contact details on your EOB or the denial notice.
Practical habits while this is running.
Keep one folder — paper or digital. Put the EOB, the denial letter, every document you send, and a log of your calls in it. Write down names and dates for each call. Ask your cancer care team's billing staff for help early. Many cancer centers have a person whose whole job is this kind of work.
Keep your treatment talk apart from your billing talk. A denial is about payment, not care. What treatment you should get is a question for your doctors. Still, it is worth asking them if anything about your plan changes while the appeal is pending.
Words to know
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Common questions
Is a denied EOB the same as a bill?
No. CMS describes an Explanation of Benefits as a notice from your health plan showing the costs of your care, while the bill is what the provider sends asking for payment. Wait until you have both and compare them.
What do I put in the appeal?
HealthCare.gov says to complete all forms your insurer requires, or write a letter that includes your name, claim number and insurance ID number, and to submit supporting documents such as a letter from your doctor and relevant medical records.
How long do I have?
You have 180 days — about six months — from the date you receive the denial notice to file an internal appeal.
What if the denial is about care I need right away?
You can ask for an expedited review. For urgent care cases the insurer must decide within 72 hours, and a final decision on an expedited appeal must come as quickly as your medical condition requires and at least within 4 business days.
Questions to ask your doctor
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Sources last checked: 2026-08-11 what this meansLast updated: 2026-08-11Next planned review: 2027-08-11
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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