You went to an in-network hospital. You followed all the rules. Then a bill arrived from an anesthesiologist, radiologist, or ER doctor you never chose—for thousands of dollars your insurance refuses to pay in full. This is balance billing, and it has been one of the most common and damaging medical billing abuses in the US. NSA violations resulted in an estimated $1.2 billion in illegal charges intercepted in 2025. Here is exactly what balance billing is, when it is illegal under the No Surprises Act, and how to fight it step by step.

1. What balance billing is (with a real example)

Balance billing is the practice of charging a patient the gap between a provider’s full billed rate and the amount the insurance company paid. It happens almost exclusively with out-of-network providers, because in-network providers have signed contracts agreeing to accept the insurance-allowed amount as payment in full.

Balance Billing Example — Out-of-Network Anesthesiologist
Anesthesiologist billed amount $4,800.00
Your insurance’s allowed amount $1,900.00
Insurance paid (80% of allowed amount, after deductible met) $1,520.00
Your coinsurance (20% of allowed amount) $380.00
Balance bill: what the provider bills you beyond your coinsurance $2,900.00
WHAT YOU SHOULD LEGALLY OWE (if NSA applies) $380.00

In this example, the patient went to an in-network hospital for surgery and never chose the anesthesiologist—the hospital assigned one who was out-of-network. Under the No Surprises Act, the patient owes only their in-network cost-sharing ($380). The $2,900 balance bill is illegal.

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Balance billing is legally permitted when you knowingly and voluntarily choose an out-of-network provider for non-emergency care: you have a PPO plan that allows out-of-network benefits, you select a specific out-of-network specialist with full knowledge of their status, the provider is not an ancillary provider at an in-network facility, and you did not sign an NSA consent waiver under duress. In this scenario, the provider can charge you their full rate minus what insurance pays.

3. When balance billing is illegal: the No Surprises Act

The No Surprises Act (NSA), effective January 1, 2022, prohibits balance billing in three specific situations:

SituationNSA ProtectionWhat You Owe
Emergency care at any facilityFull protection regardless of network statusIn-network cost-sharing only
Non-emergency care at in-network facility by out-of-network provider you did not chooseProtected unless you sign a valid consent waiverIn-network cost-sharing only
Air ambulance servicesFull protectionIn-network cost-sharing only
Ground ambulanceNOT covered by NSA (major gap)Subject to state law; may be balance billed
Voluntary out-of-network careNot protected (you chose OON provider)Full balance bill allowed

The most common NSA situation is the ancillary provider trap: you choose an in-network hospital and surgeon, but an out-of-network anesthesiologist, radiologist, pathologist, or ER physician is assigned without your input. Under the NSA, these providers cannot balance bill you. The NSA also requires insurers to send you an Advanced Explanation of Benefits (AEOB) before scheduled non-emergency care showing your estimated costs.

The NSA allows out-of-network providers to ask you to waive your protections for non-emergency, non-ancillary services only. Key rules:

  1. You are never required to sign. Refusing does not mean losing access to care at the facility.
  2. Consent must be informed. The provider must give you a good-faith cost estimate showing what you’ll owe out-of-network vs. in-network.
  3. 72-hour notice required. For scheduled procedures, the form must be provided at least 72 hours before the service (or 3 hours before for same-day scheduling).
  4. Emergency providers cannot ask you to sign. Any consent form presented in an emergency setting is invalid and unenforceable.
  5. Ancillary providers cannot ask you to sign. An anesthesiologist assigned by the hospital cannot use the consent waiver process.
If you signed under pressure in a pre-op area or emergency department: The waiver may be invalid. File a complaint with CMS at 1-800-985-3059. Consent obtained without the required advance notice or in an emergency setting is not enforceable.

5. How to spot an illegal balance bill

Ask these questions when reviewing any bill from a provider you did not explicitly choose:

  • Was this an emergency visit? If yes, the NSA applies and balance billing is prohibited.
  • Was this an ancillary provider at an in-network facility (anesthesiologist, radiologist, pathologist, ER physician, hospitalist) that you did not personally select? If yes, NSA likely applies.
  • Was this an air ambulance? If yes, NSA applies.
  • Did you sign an NSA consent waiver with proper 72-hour advance notice? If no, and the provider is balance billing you, that is likely illegal.
  • Does the bill exceed your in-network deductible, coinsurance, or copay? Compare to your EOB—the EOB shows your correct patient responsibility.

6. Step-by-step dispute process

  1. Get your EOB from your insurer. The EOB shows the claim, the allowed amount, what insurance paid, and what you legitimately owe.
  2. Compare the EOB to the provider’s bill. If the bill exceeds your “patient responsibility” on the EOB, you may have an illegal balance bill.
  3. Call the provider’s billing department. Reference the NSA and ask whether a valid NSA consent waiver was obtained. Many billing departments reduce or eliminate the balance when challenged directly.
  4. Send a written dispute. Use the template below. Send via certified mail. This creates a paper trail and may trigger hold periods under state law.
  5. File a complaint with CMS. Call 1-800-985-3059 or go to CMS.gov/nosurprises. CMS investigates and can fine providers violating the NSA.
  6. File with your state insurance commissioner. State regulators often act faster and may have additional remedies. Find your commissioner at NAIC.org.
  7. Use BillKarma. Upload your bill to generate a customized dispute letter and get guidance specific to your state.

Dispute letter template for an illegal balance bill

“I am writing to dispute the balance of $[AMOUNT] on account [ACCOUNT NUMBER]. Under the No Surprises Act (42 U.S.C. § 300gg-111), I am entitled to pay only my in-network cost-sharing amount for [emergency care / services provided by an out-of-network provider at an in-network facility]. My Explanation of Benefits from [INSURER NAME] shows my patient responsibility is $[EOB AMOUNT]. I did not sign an NSA consent waiver authorizing out-of-network billing. I request that you correct this bill to $[EOB AMOUNT] within 30 days. If unresolved, I will file a complaint with CMS and the [STATE] Department of Insurance.”

7. State protections beyond the NSA

StateKey Protection Beyond NSAGround Ambulance
New YorkNSA-style protections for fully-insured state-regulated plans; additional arbitration rightsProtected
CaliforniaAB 72 protects against OON billing at in-network facilities; comprehensive since 2017Partially protected
TexasSB 1264 provides strong protections for state-regulated plansPartially protected
IllinoisState surprise billing law for state-regulated plans, aligned with NSANot protected
All other statesFederal NSA applies; no additional state protectionsGenerally not protected

Note: The NSA applies to employer self-funded plans (ERISA plans) and federally-regulated insurance. State laws primarily cover fully-insured state-regulated plans. If your insurance is through a large employer, it is likely self-funded and governed only by federal law.

Frequently asked questions

What is balance billing?

Balance billing occurs when an out-of-network provider charges you the difference between their billed rate and the amount your insurance paid. Whether this is legal depends on the type of care, where it was received, and state law. The No Surprises Act made balance billing illegal for emergency care, ancillary providers at in-network facilities, and air ambulance.

What is the No Surprises Act?

The No Surprises Act (effective January 2022) prohibits balance billing for emergency care, out-of-network ancillary providers at in-network facilities, and air ambulance. Patients pay only their in-network cost-sharing. Providers must resolve payment disputes through an independent dispute resolution process, not by billing the patient for the difference.

Can I waive my No Surprises Act protections?

Only for non-emergency, non-ancillary services, with proper 72-hour advance notice and a good-faith cost estimate. You are never required to sign. Emergency providers and ancillary providers (anesthesiologists, radiologists) cannot ask you to waive NSA protections under any circumstances.

How do I report an illegal balance bill?

File a complaint with CMS at 1-800-985-3059 or cms.gov/nosurprises. Also file with your state insurance commissioner. Keep all documentation: the bill, your EOB, any consent forms, and records of your communications with the provider.

Does the No Surprises Act apply to ground ambulance?

No. Ground ambulance is explicitly excluded from the NSA. Some states (New York, California, Texas) have enacted their own ground ambulance balance billing protections. Check with your state insurance commissioner for current rules. For unprotected ground ambulance bills, asking for the Medicare rate as a negotiating anchor is often effective.

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