How to Read an Explanation of Benefits (EOB) — And Spot the Errors

Your insurer mails you a document after every claim. It says 'Explanation of Benefits' at the top. Most people glance at it and file it away.

That is a mistake.

Your EOB tells you exactly what your insurer paid, what they denied, and what they think you owe. If that information is wrong — and it often is — the time to catch it is before you pay the provider's bill, not after.

What an EOB Is — And What It Is Not

Your EOB is a statement from your insurer explaining how they processed a claim. It is not a bill.

Do not pay anything based on your EOB alone. Wait for the actual bill from your provider. Use your EOB to check that bill — and to catch errors before you write a check.

The Key Columns — What Each One Means

Amount Billed (or Charged): What the provider billed your insurer. This number is often much higher than reality — it is the starting point of the negotiation, not the actual price.
Allowed Amount (or Negotiated Rate): The rate your insurer has contractually agreed to pay for this service. For in-network providers, this is substantially less than what was billed.
Discount Savings: The difference between the billed amount and the allowed amount. You are not responsible for this portion — do not pay it.
Plan Paid: What your insurer actually paid the provider. Typically the allowed amount minus your share.
Your Responsibility (Member Responsibility): What you owe — your deductible, copay, or coinsurance after the insurer pays their share.
Denial Reason Code: If a claim was denied, this code tells you exactly why. Look it up — it usually also tells you exactly how to fix it.

Common EOB Denial Codes and What They Mean

CO-4: Procedure code inconsistent with modifier — a billing code error on the provider's side
CO-97: Claim not submitted on time — may be disputable if provider delay caused it
CO-119: Benefit maximum reached — you may have hit an annual plan cap
CO-197: Precertification absent — prior authorization was required but not obtained
PR-1: Deductible amount — what you owe toward your annual deductible
PR-2: Coinsurance amount — your percentage share of the allowed amount
PR-3: Copayment amount — your fixed fee for this service
OA-23: Benefit excluded from plan coverage — check your Summary of Benefits to confirm

Regulation Citation

Claim Denial Appeal Rights

ACA § 2719; 45 CFR § 147.136

If your insurer denies a claim, your EOB must explain the specific reason and tell you how to appeal. You have the right to appeal any denial — and your insurer must provide a full and fair review. The denial on your EOB is not the final word.

How to Compare Your EOB to Your Provider Bill

1
Request your itemized bill from the provider
You need the itemized bill — every CPT code and charge, line by line. Call the billing department and ask for it. Do not compare a summary bill to your EOB. You need the detail.
2
Match dates and provider names
Confirm the date of service and provider name match on both documents. A mismatch could be a billing error or an identity mix-up — both worth flagging immediately.
3
Compare the procedure codes
The CPT codes on your bill should match what your insurer processed on the EOB. A different code on the bill versus the EOB means something changed between the provider and the insurer — find out what.
4
Verify your responsibility amount
The amount your provider bills you should not exceed the 'Member Responsibility' column on your EOB. If the provider's bill is higher, that is likely a billing error. Dispute it with both the provider and your insurer.

What to Do When the Numbers Do Not Match

Start with the provider billing department. Show them both documents. Explain the discrepancy. Ask them to correct the bill.

If the issue is that your claim was processed as out-of-network when it should be in-network — call your insurer's member services directly. Ask them to reprocess the claim with the correct network status.

Document every conversation in writing. Follow up every phone call with a brief email or certified letter stating what you discussed. A paper trail matters if this escalates.

Frequently Asked Questions

Why do I get an EOB but not a bill at the same time?

Your insurer processes the claim and sends you the EOB — usually before or around the same time the provider sends their bill. The sequence: you get care, the provider bills your insurer, your insurer processes it and sends the EOB, then the provider bills you for any remaining balance. Always wait for the actual provider bill before you pay anything.

What if my EOB shows a service I did not receive?

That is a billing error — and potentially fraud. Contact your provider's billing department first and ask for an explanation. If the service was never rendered, report it to your insurer's fraud hotline and to the HHS Office of Inspector General at oig.hhs.gov. Medical billing fraud is a federal crime.

How long do I have to appeal an EOB denial?

For internal appeals, you typically have 180 days from the date on your EOB denial notice. Check the denial letter — the deadline will be listed. For urgent care, you typically have 72 hours to request expedited review. Missing the internal appeal deadline generally waives your right to that appeal level.

What does 'not medically necessary' mean on my EOB?

'Not medically necessary' means your insurer's review system determined the service did not meet their internal medical necessity criteria — not necessarily that it was clinically inappropriate. Your treating physician's letter explaining why the treatment was necessary is strong evidence for an appeal. External reviewers frequently overturn these denials when treating doctors document the clinical rationale clearly.

Can I get EOBs for past claims?

Yes. Log in to your insurer's member portal — most store EOBs for 2-3 years. You can also call member services and ask for copies to be mailed. Under HIPAA, you also have the right to request your medical records from providers, which helps you verify what services were actually delivered.

What if my employer plan processes my claim differently than I expected?

Employer-sponsored ERISA plans are governed by the plan's own documents — your Summary Plan Description (SPD) controls your benefits. Request your SPD from HR. If your claim was processed inconsistently with the SPD, you have the right to appeal under ERISA § 503. You can ultimately file a civil action in federal court if the plan wrongly denies your benefits.