EOB & Medical Billing Glossary

Explanation of Benefits (EOB)

A statement from your health insurer explaining how it processed a claim. An EOB is not a bill — it's a summary showing what was billed, what your plan allows, what insurance paid, and what the insurer calculates as your patient responsibility. Medicare.gov's own consumer guidance describes the EOB as a notice to review and check for mistakes, not a request for payment.

Source: Medicare.gov — Explanation of Benefits (EOB)

Patient Responsibility

The dollar amount your insurer calculates that you owe for a claim, after applying your deductible, copay, or coinsurance. This is the single most important figure on your EOB — it's the number to compare directly against what your provider's bill says you owe. If the two don't match, that gap is worth investigating before you pay.

Allowed Amount

The negotiated rate your insurance plan actually recognizes for a service, usually lower than what the provider originally billed. If your provider is in-network, you're generally not responsible for the difference between the billed amount and the allowed amount — that gap is written off under the insurer's contract with the provider.

Amount Billed

The original charge the provider submitted, before any insurance adjustment. This is often significantly higher than what the insurer ultimately allows or pays — a large gap here isn't necessarily wrong, but it's not what you'll actually owe either.

Amount Paid (by Insurance)

What your insurance company actually paid the provider for the claim. A simple check worth doing yourself: allowed amount minus amount paid should equal your patient responsibility. If it doesn't on your own EOB, that's worth a call to your insurer.

Deductible

The amount you must pay out of pocket for covered services before your insurance plan starts paying its share, for the plan year.

Copay (Copayment)

A fixed dollar amount you pay for a covered service at the time you receive it, regardless of that service's total cost.

Coinsurance

Your share of a covered service's cost, expressed as a percentage, after you've met your deductible — for example, paying 20% while your plan covers the remaining 80%.

Remark Code

A short code next to a line item on your EOB, matched to an explanation elsewhere on the page or a linked code glossary, describing why that item was adjusted, reduced, or denied — for example, "not a covered service" versus "missing prior authorization" are very different problems with different next steps.

Balance Billing

When a provider bills you directly for the difference between what they charged and what your insurance paid, beyond your normal cost-sharing. Federal law (the No Surprises Act) and some state laws restrict this in specific situations — particularly emergency care and certain out-of-network providers at in-network facilities.

See our free quiz to check whether these protections likely apply to your situation.

Good Faith Estimate (GFE)

A written estimate of expected charges that uninsured and self-pay patients are generally entitled to receive before a scheduled medical service. If your final bill comes in $400 or more above this estimate, you may be eligible for a federal dispute process.

Check with our free Good Faith Estimate calculator.

Itemized Bill

A detailed statement listing every individual charge for a visit or stay, rather than just one summary total. Requesting this instead of accepting a summary bill is one of the fastest ways to spot duplicate charges or billing errors.