Skip to main content

Medical billing reference

Medical billing and health insurance glossary

These plain-English definitions explain terms that commonly appear on U.S. medical bills, health-plan documents, and Explanations of Benefits. Your own plan document, notice, and applicable law control when a definition differs.

Last reviewed by Jason Ramirez, a web professional and product founder, not a clinician, attorney, insurer, certified medical coder, or billing specialist.

Browse all 12 terms

Allowed amount

The amount a health plan uses as the payment basis for a covered service under its rules.

Chargemaster

A hospital's internal list of gross charges for items and services, not a prediction of what a particular patient will owe.

Deductible

An amount a member may need to pay for covered services before the plan begins paying for services subject to that deductible.

Copay

A fixed cost-sharing amount a plan assigns to a covered visit, service, or item under specified conditions.

Coinsurance

Percentage-based cost sharing that is generally calculated from a plan's allowed amount for a covered service.

Out-of-pocket maximum

A plan-year limit on eligible member cost sharing for covered services under the plan's rules.

Prior authorization

A health plan's advance review that may be required before certain services, prescriptions, or supplies will be considered for coverage.

Balance billing

A provider's attempt to bill a patient for a difference not paid by the health plan, subject to contracts and applicable protections.

Surprise billing

Unexpected out-of-network billing that may be restricted by federal or state protections in specified situations.

Good Faith Estimate

A written estimate of expected charges generally provided to uninsured or self-pay people before scheduled care or upon request.

Itemized bill

A provider statement that separates billed items or services instead of showing only a summary total.

Continue with a practical guide

Sources, updates, and corrections

Definitions were independently written and checked against current primary guidance from CMS and HealthCare.gov on October 16, 2026. Rules and terminology can change, and a health plan may define a term more specifically. Each term page links the sources used for that definition.

See the editorial and corrections policy or report a possible correction. Do not send a medical bill or personal health information by email.