eob-a-plain-english-guide">What Is an Explanation of Benefits (EOB)? A Plain-English Guide

After you receive medical care, your insurance company sends you an Explanation of Benefits (EOB). It's one of the most confusing documents in healthcare — but also one of the most important. Understanding your EOB can help you spot billing errors, detect fraudulent charges, and identify when to file an appeal.

What Is an EOB?

An Explanation of Benefits (EOB) is a document sent by your health insurance company after you (or your provider) submits a claim. It explains:

• What services were claimed
• How much the provider billed
• How much your insurer paid
• How much you owe (your cost-sharing)
• Why any portion wasn't paid

Critical point: An EOB is NOT a bill. You don't pay the EOB. You pay your provider's separate billing statement. However, if the EOB and your bill disagree, investigate — it may indicate a billing error or fraud.

How to Read an EOB: Section by Section

1. Patient and Provider Information

Top section identifies:

• Your name and insurance ID
• The provider or facility that rendered services
• Dates of service
• Claim number (save this — you'll need it if you appeal)

2. Services Rendered

A table listing each billed service with:

• CPT code / procedure code: The standardized code identifying the specific service (e.g., 99213 = office visit, moderate complexity)
• Description: Plain-language description of the service
• Date of service

3. Billed Amount vs. Allowed Amount

• Billed amount (Charged amount): What the provider billed — often dramatically higher than what's paid
• Allowed amount (Eligible amount / Maximum allowable): The maximum your plan will consider for payment, based on your plan's fee schedule or contracted rate
• Discount (Write-off): If the provider is in-network, they've agreed to accept the allowed amount and write off the rest

4. What Your Insurance Paid

• Plan paid / Insurance paid: The portion your insurer paid to the provider
• This is usually: Allowed Amount minus your cost-sharing (deductible + copay + coinsurance)

5. Your Responsibility (Patient Cost)

• Deductible applied: Portion applied toward your annual deductible
• Copay: Fixed dollar amount you owe for the visit
• Coinsurance: Your percentage (e.g., 20% of the allowed amount after deductible)
• Not covered / Non-covered amount: Services your plan doesn't cover at all

6. Denial or Adjustment Codes

If any service was not covered, you'll see reason codes:

• CARC (Claim Adjustment Reason Codes): Standard codes explaining adjustments (e.g., CARC 4 = "The service is not covered by this plan")
• RARC (Remittance Advice Remark Codes): Additional explanation codes
• CO, OA, PI, PR codes: Type of adjustment (CO = contractual obligation; PR = patient responsibility)

Common codes to know:

• CARC 96: Non-covered charge
• CARC 50: These are non-covered services because this is not deemed a 'medical necessity'
• CARC 16: Claim/service lacks information needed for adjudication

What to Do If Your EOB Shows a Denial

Step 1: Check the Denial Code

Locate the CARC/RARC code and look it up on the Washington Publishing Company (WPC) website (wpc-edi.com). Understand specifically why the claim was denied.

Step 2: Compare EOB to Your Bill

If your provider's bill is higher than your EOB shows as your responsibility:

• If in-network: The provider must accept the allowed amount. Any attempt to bill you more (balance billing) may be a violation of your plan contract.
• If out-of-network: Balance billing may be permitted, but the No Surprises Act may apply for emergency care.

Step 3: Check for Billing Errors

Common errors that cause incorrect EOBs:

• Wrong procedure code (CPT error)
• Wrong diagnosis code (ICD-10 error)
• Wrong date of service
• Upcoding (billed a more complex service than performed)
• Duplicate billing
• Bundling errors (billing component codes instead of a single bundled code)

Step 4: File an Appeal If Benefits Were Wrongly Denied

If the EOB shows a denial that you believe is incorrect:

1. Note the claim number and denial reason code
2. File a formal appeal with your insurer (internal appeal)
3. Your denial letter (which accompanies the EOB or is sent separately) must include appeal rights information

Electronic EOBs (eEOBs) and Patient Portals

Most insurers now provide EOBs through online portals. Medicare provides the Medicare Summary Notice (MSN) — the Medicare equivalent of an EOB — quarterly through Medicare.gov.

Fight Back With ClaimBack

If your EOB shows a denial and you want help appealing, ClaimBack generates professional appeal letters that directly address the denial codes on your EOB.

Start your free appeal at ClaimBack →

Related Reading

• Medical Billing Errors: How to Spot Them and Appeal
• Common Reasons Insurance Claims Are Denied
• How to Write an Insurance Appeal Letter