Fonteum Data GlossaryPayer
Explanation of Benefits: Definition and Healthcare Context
Full name: Explanation of Benefits (EOB)
An Explanation of Benefits (EOB) is a document sent by a health insurer to a covered member and provider after a claim is processed, explaining what services were billed, what the plan paid, what was denied, and what the member may owe. EOBs are not bills; they are informational summaries. Under the CMS Interoperability and Patient Access Final Rule, Medicare Advantage and Medicaid plans must make EOB and claims data available to beneficiaries through FHIR-based Patient Access APIs, enabling members to retrieve their claims history electronically.
- Source file
- Not reported
- Published
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- Retrieved
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- Snapshot
- Not retained for this reference page
- Re-check
- CMS: Patient Access API overview
- Data as of
- Not reported
Last updated: 2026-07-11Reviewed by: Dr. Jennifer Montecillo, MD — Gullas College of Medicine, 2019. Non-practicing medical reviewer.
How it’s used
- CMS PECOS Medicare Provider Enrollment: enrolled providers receive Medicare EOBs through the MAC's remittance system (as ERAs), tying payment explanations to PECOS-enrolled NPI records.
- CMS Interoperability and Patient Access Final Rule: Medicare Advantage and Medicaid plans must expose EOB data through Patient Access FHIR APIs, the interoperability standard Fonteum's data layer mirrors.
- ASC X12 835 / ERA: the provider-side electronic counterpart of a member EOB is the 835 remittance, linking payment explanations to the enrolled provider's NPI.
Frequently asked questions
- What is an EOB?
- An Explanation of Benefits (EOB) is a statement from your insurer that explains what was billed for a service, what the plan paid, and what — if anything — you may owe.
- Is an EOB the same as a bill?
- No. An EOB is an informational document from your insurer. An actual bill comes from the provider and may differ from the EOB.
- Can I access my EOB electronically?
- Under the CMS Interoperability Rule, Medicare Advantage and Medicaid plans must provide FHIR-based APIs so members can download their claims and EOB data.