Medicare Part B assignment and the limiting charge

What “assignment” means

Medicare Part B pays for many physician and outpatient services. The program sets an approved amount for covered services. A provider who accepts assignment agrees that this amount is the full charge for the service, subject to the deductible, coinsurance, and other ordinary beneficiary obligations. The provider submits the claim to Medicare and generally cannot collect more than the applicable patient share for the covered service.

Assignment does not mean Medicare pays 100 percent. A beneficiary may still owe the Part B deductible, then usually owes coinsurance under Original Medicare. Supplemental coverage may pay some of that amount depending on its terms. The key point is that the provider cannot add an unrestricted extra amount above the approved charge when assignment applies.

Participating and nonparticipating providers

A participating provider signs an agreement to accept assignment for all Medicare-covered services during the participation period. A nonparticipating provider has not made that all-claims commitment. However, a nonparticipating provider can still choose assignment for a particular claim. The beneficiary should ask whether the provider accepts assignment for the service before treatment when practical.

This status affects the provider’s billing flexibility, not whether the beneficiary is enrolled in Medicare. A nonparticipating provider is still subject to Medicare rules for covered services and may have to submit claims. The patient should not equate “nonparticipating” with “Medicare does not cover this service.” Coverage and assignment are separate questions.

The limiting charge

For many covered Part B services, a nonparticipating provider who does not accept assignment may charge the beneficiary up to a statutory limiting charge. The limit is generally 115 percent of the Medicare-approved amount applicable to nonparticipating providers. Because the underlying nonparticipating amount can differ from the participating amount, a simple “15 percent above any number on the bill” shortcut can mislead.

The limiting charge applies to specified covered services and has exceptions. It is not an authorization to charge 115 percent of any submitted price for every medical service. It does not apply in the same way to services that Medicare does not cover, and some categories or circumstances have different rules. Check Medicare’s current explanation and the service-specific limit rather than calculating from an unrelated retail charge.

A provider that accepts assignment cannot use the limiting charge to add a surcharge. The agreed Medicare-approved amount is the full allowed charge, and the beneficiary is responsible only for the standard deductible and coinsurance, subject to any secondary coverage. That is why asking about assignment before a planned visit can help a patient estimate exposure.

How the claim flows

With assignment, the provider generally files the claim and waits for Medicare’s payment, then bills the beneficiary for the allowed deductible or coinsurance. Without assignment, the patient may be asked to pay at the visit and the provider submits a claim; Medicare then sends the beneficiary the share it pays, with the patient responsible for the provider amount up to the applicable limit. Actual claim workflows can vary.

The Medicare Summary Notice reports what Medicare processed, what it paid, and what the beneficiary may owe. It is not itself an invoice from the provider. Compare the notice with the provider’s itemized bill. If the provider’s amount appears above the limiting charge or contradicts an assignment commitment, ask the billing office to review the claim and contact Medicare if needed.

Assignment, coverage, and medical necessity

Assignment answers the price-limit question after a service is treated as a Medicare-covered service. It does not decide whether a service is medically necessary, whether a frequency limit applies, or whether a prior authorization rule is met. A provider may accept assignment yet Medicare may deny a service under coverage rules. In that case the beneficiary’s liability depends on notice requirements and other Medicare rules.

Before receiving a service that may not be covered, a patient may receive an Advance Beneficiary Notice. An ABN can explain that Medicare may not pay and allow the beneficiary to make an informed choice. A signature is not a universal waiver of every protection. The reason for the notice, its wording, and applicable claim rules matter.

Private contracts are a different situation

Some physicians may opt out of Medicare and enter private contracts for services furnished to Medicare beneficiaries, subject to Medicare’s opt-out rules. A private contract is different from ordinary nonparticipating status and the limiting charge framework. The beneficiary should confirm whether the physician has opted out and understand the written contract before receiving care.

A patient should not assume that every out-of-network or nonparticipating encounter is a private contract. The category has formal requirements. If a provider requests a private payment agreement, the patient can ask whether the provider participates, accepts assignment, or has opted out, and then review the resulting billing rules.

Worked comparison

Assume Medicare approves a covered service at $100 and a participating provider accepts assignment. The provider accepts $100 as the full allowed charge. If the deductible has already been met and coinsurance is 20 percent, the patient share under Original Medicare would ordinarily be $20 before secondary coverage.

If a nonparticipating provider does not accept assignment, the applicable nonparticipating approved amount and limiting charge rules must be used. Do not simply take the participating $100 and add 15 percent without checking the official amount and the service category. The question may be testing the concept rather than asking for a complete claim calculation.

What to remember

Assignment is a provider’s agreement to accept the Medicare-approved amount for a covered claim. Participation is an all-claims commitment for participating providers; nonparticipating providers can decide assignment claim by claim. The limiting charge caps many charges by nonparticipating providers who do not accept assignment. Deductibles, coinsurance, coverage determinations, ABNs, and opt-out private contracts remain separate parts of the analysis.

Assignment can change from one visit to another

A physician’s participation status and a particular claim’s assignment status are related but not identical. Participating providers accept assignment on Medicare claims during their participation agreement. A nonparticipating provider may accept assignment for one service and decline it for another. Ask about the specific clinician and service, especially when a group practice includes clinicians with different Medicare arrangements.

For a scheduled service, the Medicare Care Compare directory and the provider office can help establish participation, but confirm directly when the price matters. A directory listing may not answer whether a nonparticipating provider intends to accept assignment on a particular claim. Record the answer and ask how the office estimates the beneficiary’s share.

If a beneficiary believes a provider exceeded the applicable limit, first request an itemized bill and the Medicare-approved amount for each service. Billing codes, modifiers, and setting can change the allowed amount. Medicare can explain its claim determination, while the provider can correct a coding or billing error. Avoid comparing an entire visit bill with one headline fee.