Health Insurance
How to Read an Explanation of Benefits (EOB)
By the PolicyZen Team · Updated March 2026 · 8 min read
After any medical visit, you'll eventually receive an Explanation of Benefits from your insurer. Most people glance at it, assume it's a bill, and file it away — or throw it out. It's not a bill. It's a detailed accounting of how your claim was processed. And buried in that document are the numbers that determine exactly what you owe, what your insurer paid, and whether any errors were made.
Billing errors in healthcare are common. Studies estimate that 30–80% of medical bills contain errors. Your EOB is the tool for catching them.
The EOB is NOT a bill. It's a statement from your insurance company explaining what they paid and why. The actual bill comes from your provider. But the EOB tells you what the bill should say — and if the provider's bill is higher than what the EOB says you owe, that's a potential error.
The Key Fields on Every EOB
Billed Amount / Submitted Charge
$2,400
What the provider charged. This is their "list price" — almost never what anyone actually pays.
Allowed Amount / Negotiated Rate
$1,100
The contracted rate your insurer negotiated with in-network providers. The entire claim is based on this number, not the billed amount.
Plan Paid / Insurance Paid
$880
What your insurance company actually paid the provider (after applying your deductible and coinsurance to the allowed amount).
Patient Responsibility
$220
What you owe. This is the number that matters most. It should match — or be close to — what your provider bills you.
Deductible Applied
$0
How much of this claim was applied toward your annual deductible. Tracks your deductible progress over the year.
Coinsurance / Copay
$220
Your share of the allowed amount after the deductible. Typically 20% of the allowed amount for in-network services.
The Math Behind It
Here's how those numbers connect for an in-network visit where your deductible is already met:
- Provider bills $2,400 (their listed price)
- Insurer's contracted rate: $1,100 (the allowed amount)
- You pay 20% coinsurance of the allowed amount: $220
- Insurer pays 80%: $880
- The remaining $1,300 (difference between billed and allowed): written off — in-network providers agree to accept the allowed amount as payment in full
The provider cannot bill you the $1,300 difference. That's what "in-network" means: the provider accepts the insurer's negotiated rate as the total payment.
Remark Codes: Why Claims Are Adjusted or Denied
Every line item on an EOB typically includes one or more remark codes — alphanumeric codes that explain why a service was adjusted, denied, or paid differently than billed. These codes are standardized nationally (CARC — Claim Adjustment Reason Codes).
The codes that say "CO" (Contractual Obligation) are adjustments that are not your responsibility — the provider writes them off. The codes that say "PR" (Patient Responsibility) are what you owe. If a denial or adjustment looks wrong, the remark code tells you what to cite when you call your insurer.
How to Spot Errors
Medical billing errors are genuinely common. Here's what to look for:
- Wrong date of service: Compare the EOB date to your actual visit date. Mismatches can cause a claim to be processed under the wrong benefit year (before or after your deductible resets)
- Wrong procedure code: Providers sometimes bill with incorrect CPT codes. A code that doesn't match your actual service may result in incorrect cost-sharing or denial
- Duplicate billing: The same service billed twice (common with lab work processed in multiple places)
- Upcoding: A more complex (and expensive) service billed than what was actually performed
- Out-of-network processing: If you used an in-network provider but the claim was processed at out-of-network rates, something went wrong with credentialing or claim routing
- Wrong patient: Rare but happens — especially with common names or family members on the same plan
Never pay a provider bill before receiving the EOB for that service. Wait for your insurer to process the claim and send the EOB. Then compare the "Patient Responsibility" on the EOB to what the provider bills you. If the provider's bill exceeds your EOB patient responsibility, call the billing department and cite the EOB before paying anything.
What to Do When Something Looks Wrong
- Call your insurer first. Use the member services number on your insurance card. Ask them to explain the specific remark code and adjustment. Sometimes it's correct but confusing; sometimes it's an error they can fix.
- Call the provider's billing department. If the insurer confirms the claim was processed correctly but the provider's bill doesn't match, the billing department can reconcile it.
- Request an itemized bill from the provider. You're entitled to an itemized bill showing every charge line by line. Compare each line to the EOB.
- File an appeal if the claim was denied. Every EOB denial comes with appeal rights. Your EOB will note the appeals deadline — typically 180 days from the EOB date. Don't miss it.
Frequently Asked Questions
Do I get an EOB for every medical visit?
Yes — for every claim your provider submits to your insurer, you should receive an EOB. You may receive them by mail or through your insurer's online portal. Some insurers let you set notification preferences. If you had a visit and never received an EOB, log in to your insurer's member portal and check claim history — it may be there even if the paper EOB wasn't mailed.
How long should I keep EOBs?
Keep EOBs for at least one year, or until you've confirmed the corresponding provider bill was paid correctly. For tax purposes, if you're deducting medical expenses or tracking HSA-eligible expenses, keep EOBs for 7 years (consistent with general tax record retention). Digital copies from your insurer's portal are acceptable.
The EOB says I owe $0 but the provider billed me $300. What do I do?
Don't pay immediately. Call the provider's billing department and tell them your EOB shows $0 patient responsibility. Ask them to review the claim. This is usually either a billing error, a timing issue (the provider billed before the insurer processed the claim), or the provider is billing for a portion not covered by insurance that the EOB doesn't reflect. Get a written explanation before paying anything that contradicts your EOB.
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