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  1. Fonteum
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  3. Glossary
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  5. Balance Billing
Fonteum Data GlossaryPayer

What is balance billing?

Balance billing is when an out-of-network provider bills the patient for the difference between the provider's charge and what the insurer paid — the 'balance.' The No Surprises Act prohibits it for emergency services, air ambulance transport, and non-emergency care at in-network facilities without prior informed choice; Medicare and Medicaid have long-standing limits of their own.

Full name: Balance Billing / Surprise Billing

Short explanation

Balance billing is the practice by which an out-of-network provider bills a patient for the difference between the provider's charge and the amount the patient's insurer pays — the 'balance'. The No Surprises Act prohibits balance billing in specified circumstances: emergency services, air ambulance transport, and non-emergency services at in-network facilities when the patient had no prior informed choice of provider. Medicare and Medicaid programs have long-standing limits on provider balance billing.

Last updated: 2026-07-11Reviewed by: Dr. Jennifer Montecillo, MD — Gullas College of Medicine, 2019. Non-practicing medical reviewer.

How it’s used

  • CMS NPPES NPI Registry: provider network status — derived from NPPES data and supplemented by insurer MRF directory data — is a key input in balance-billing compliance determinations.
  • No Surprises Act: the NSA prohibits balance billing for emergency and specified out-of-network services, the statutory boundary Fonteum's surprise-billing compliance research applies.
  • Insurer machine-readable files (Transparency in Coverage Rule): payer MRFs publish in-network rates that determine when a patient bill crosses into prohibited balance billing.

Frequently asked questions

What is balance billing?
Balance billing occurs when an out-of-network provider charges a patient for the difference between their billed rate and what the patient's insurer paid.
Is balance billing legal?
In many circumstances it is now prohibited under the No Surprises Act for emergency services, air ambulance, and unplanned out-of-network care at in-network facilities.
What is the difference between balance billing and surprise billing?
Surprise billing refers specifically to unexpected balance bills received after the fact — typically after emergency or inadvertent out-of-network care.

Related terms

  • No Surprises Act
  • Prior Authorization
  • Machine-Readable File
  • Medicare
  • Medicaid

Authoritative sources

  • CMS: No Surprises Act — balance billing protections↗
  • CMS: Understanding your bill and preventing surprise bills↗
← All glossary terms

What’s on file, by the numbers

Platform snapshot · 2026-07-15

13.4Mproviders & companiesProviders, organizations, owners, and facilities on file
26.2Msource-linked factsSource-linked field facts in the dated platform snapshot
—sources liveCrosswalk-resolved sources with a proved content transition in the preceding 45 days
111sources integratedActive registry rows; integration does not establish a load
13state Medicaid jurisdictionsDistinct states represented in the state-exclusions serving table

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The platform records table row counts daily. Those observations detect local drift; they do not imply that an upstream publisher released or Fonteum ingested new data that day.

Named medical review

Reviewed by Jennifer Montecillo, MD, medical reviewer. Non-practicing medical reviewer.

Read the full provenance and attestation methodology →

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Reviewed by Jennifer Montecillo, MD, medical reviewer. Non-practicing medical reviewer.

© 2026 Fonteum LLC. All rights reserved.

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A public-records graph that exposes source and observation metadata where supplied.

Fonteum's provenance ledger contained 26.2M source-linked facts on July 12, 2026. All but 14 carried a source-file SHA-256; 0 linked deterministically to a signature. Inspect a supplied snapshot id at fonteum.com/verify · source-mark coverage and limitations.
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