How to Read an Explanation of Benefits (EOB) When You Have Cancer

After a cancer diagnosis, your mailbox fills up fast. Appointment reminders. Lab results. And a steady stream of documents from your insurance company that say — in large, reassuring letters — THIS IS NOT A BILL.

That document is your Explanation of Benefits, or EOB. And while it is not a bill, it is one of the most important pieces of paper you will receive during cancer treatment.

Most people glance at it and set it aside. That is a costly mistake.

An EOB is a summary your insurance company sends after a medical claim is processed. It shows:

• What your provider billed
• What your insurance company allowed (the negotiated rate)
• What your insurance paid
• What you owe — and why

It is not a bill. Your provider will send a separate bill. But the EOB tells you whether that bill is correct.

During cancer treatment, you may receive dozens of EOBs per month — one for every lab draw, imaging scan, infusion, specialist visit, and procedure. The volume is overwhelming, and errors are common.

Studies have found that medical billing errors occur in up to 80% of hospital bills. Cancer treatment, with its complexity and high volume of claims, is particularly prone to mistakes. Common errors include:

• Services billed that were never provided
• Duplicate charges for the same service
• Incorrect diagnosis or procedure codes
• In-network providers billed as out-of-network
• Claims denied for services that should be covered
• Coordination of benefits errors when you have secondary insurance

Each of these errors can result in you being charged more than you legally owe. The only way to catch them is to read your EOBs.

EOBs vary by insurer, but every one contains the same core sections.

At the top, you will find:

• Patient name — confirm this is you (identity mix-ups happen)
• Member ID — your insurance ID number
• Provider name — who provided the service
• Date of service — when the service was rendered
• Claim number — the unique identifier for this claim (save this for any follow-up calls)

What to check: Make sure the date of service matches an appointment you actually had. If you see a date when you were not seen, that is a red flag.

This section lists what was billed, usually as a procedure code (CPT code) and a brief description.

Common codes you may see during cancer treatment:

• 99213 / 99214 — Office visits (different complexity levels)
• 96413 / 96415 — Chemotherapy infusion
• 77386 / 77387 — Radiation treatment delivery
• 88305 — Surgical pathology (biopsy analysis)
• 80053 — Comprehensive metabolic panel (blood work)

What to check: Does the description match what you received? If you had a 30-minute infusion but the code reflects a 3-hour infusion, that is a discrepancy worth investigating.

This is what your provider charged before any insurance adjustments. It is often much higher than what anyone actually pays — this is the "sticker price" in a system where negotiated rates do the real work.

What to check: You do not need to pay the billed amount. Do not panic at this number.

This is the amount your insurance company has agreed to pay for this service under your plan's contract with the provider. It is almost always lower than the billed amount.

If your provider is in-network, the allowed amount is the contractually negotiated rate. Your provider cannot bill you more than this amount — the difference between the billed amount and the allowed amount is written off.

If your provider is out-of-network, the allowed amount may be based on a different calculation (often a percentage of Medicare rates), and you may be responsible for the difference — called balance billing.

What to check: Is your provider listed as in-network? If you specifically chose an in-network provider and they are being processed as out-of-network, call your insurer immediately.

This is what your insurance company actually paid the provider.

What to check: Does this match what you expected based on your plan's coverage? If your plan covers 80% of in-network services after your deductible and you have met your deductible, the plan should be paying 80% of the allowed amount.

This is what you owe. It is broken down into:

• Deductible — the amount applied toward your annual deductible
• Copay — a fixed amount per visit or service
• Coinsurance — your percentage share of the allowed amount after the deductible is met
• Not covered — amounts your plan does not cover at all

What to check: This is the number that should match your provider's bill. If your provider bills you more than this amount, you may be being overbilled.

If a claim was denied or partially denied, the EOB will include a reason code. Common denial reasons include:

• CO-4 — Procedure code inconsistent with modifier
• CO-11 — Diagnosis inconsistent with procedure
• CO-29 — Claim filed after time limit
• PR-204 — Service not covered under this plan
• CO-97 — Payment included in another service

What to check: Not all denials are correct. Many are administrative errors that can be overturned on appeal. A denial reason of "not medically necessary" is almost always worth appealing with documentation from your oncologist.

When an EOB arrives, work through it in this order:

Step 1: Match it to a real appointment. Pull up your calendar or appointment records. Does the date of service correspond to a visit you actually had?

Step 2: Verify the provider. Is the name correct? Is the in-network/out-of-network designation accurate?

Step 3: Check the procedure codes. Do the services listed match what you received? If you are unsure what a code means, the American Medical Association's CPT code lookup or a quick search will tell you.

Step 4: Confirm your responsibility. Note the "patient responsibility" amount. When the provider's bill arrives, it should match.

Step 5: Track your deductible and out-of-pocket maximum. Most EOBs include a running total. Keep a separate log — insurers sometimes make errors in these running totals.

Step 6: Flag anything that does not match. Set aside any EOB where the date, provider, service, or amount does not look right.

Call your provider's billing department. Reference the EOB claim number and the "patient responsibility" amount. Ask them to reconcile the difference. If the provider insists on the higher amount, escalate to your insurer.

You have the right to appeal. Every insurer is required to have an appeals process. Steps:

1. Request the specific denial reason in writing
2. Ask your oncologist or specialist to write a letter of medical necessity
3. Submit a formal appeal within the deadline (usually 30–180 days)
4. If the internal appeal fails, request an external review — an independent organization reviews the denial

This is potential fraud. Contact your insurer's fraud hotline (listed on your insurance card) and your provider's billing department. Do not pay for services you did not receive.

This is a common error, especially with hospital-based specialists (anesthesiologists, radiologists, pathologists) who may not be in-network even when the hospital is. Under the No Surprises Act, you have protections against unexpected out-of-network bills in many circumstances. Contact your insurer and ask them to reprocess the claim.

During active cancer treatment, you may receive 20–50 EOBs per month. A simple system prevents overwhelm:

• Create a folder (physical or digital) for each calendar year
• File by date of service, not date received
• Keep every EOB until you have confirmed the corresponding provider bill matches and you have paid it
• Never discard EOBs until the claim is fully resolved and any appeals are closed
• Keep EOBs for at least seven years — you may need them for tax purposes (medical expense deductions) or future insurance disputes

Reading EOBs is time-consuming, confusing, and emotionally draining when you are also managing treatment. A cancer navigator can:

• Review EOBs alongside you and flag discrepancies
• Help you understand denial reason codes
• Draft appeal letters with supporting documentation
• Coordinate with your care team to obtain medical necessity letters
• Track your deductible and out-of-pocket maximum across multiple insurers
• Identify patterns of billing errors across providers

At Beacon Cancer Navigation, financial navigation is a core part of what we do. We do not provide legal or financial advice — but we help you understand what you are looking at, ask the right questions, and take the right next steps.

Is an EOB the same as a medical bill?

No. An EOB is sent by your insurance company and shows how a claim was processed. A medical bill is sent by your provider and shows what you owe them. The two should match — if they do not, investigate before paying.

How long do I have to appeal a denied claim?

Deadlines vary by insurer and plan type, but most plans allow 30–180 days from the denial date. Check your plan documents or call your insurer. Do not wait — missing the deadline forfeits your right to appeal.

What if I have both primary and secondary insurance?

Your primary insurer processes the claim first. The EOB from your primary insurer is then sent to your secondary insurer, which processes the remaining balance. You should receive EOBs from both. Coordination of benefits errors — where one insurer does not properly account for the other's payment — are common and worth checking carefully.

Can I get my EOBs online?

Yes. Most insurers have online portals where you can view and download EOBs. Setting up online access is worth doing early in treatment — it is faster than waiting for mail and easier to search and organize.

What does "applied to deductible" mean on my EOB?

It means the amount was counted toward your annual deductible but not yet paid by insurance. Once you meet your deductible, insurance begins paying its share. Tracking this running total helps you anticipate when your out-of-pocket costs will decrease.

Beacon Cancer Navigation provides non-clinical logistical and supportive guidance. We do not provide medical advice, legal advice, or financial advice. For questions about your specific insurance coverage, contact your insurer directly or consult a licensed insurance professional or patient advocate.