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What is Medicare assignment and how does it work?

​Because Medicare decides how much to pay providers for covered services, if the provider agrees to the Medicare-approved amount, even if it is less than they usually charge, they’re accepting assignment.

A doctor who accepts assignment agrees to charge you no more than the amount Medicare has approved for that service. By comparison, a doctor who participates in Medicare but doesn’t accept assignment can potentially charge you up to 15 percent more than the Medicare-approved amount.

That’s why it’s important to ask if a provider accepts assignment before you receive care, even if they accept Medicare patients. If a doctor doesn’t accept assignment, you will pay more for that physician’s services compared with one who does.

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How much do I pay if my doctor accepts assignment?

If your doctor accepts assignment, you will usually pay 20 percent of the Medicare-approved amount for the service, called coinsurance, after you’ve paid the annual deductible. Because Medicare Part B covers doctor and outpatient services, your $240 deductible for Part B in 2024 applies before most coverage begins.

All providers who accept assignment must submit claims directly to Medicare, which pays 80 percent of the approved cost for the service and will bill you the remaining 20 percent. You can get some preventive services and screenings, such as mammograms and colonoscopies, without paying a deductible or coinsurance if the provider accepts assignment. 

What if my doctor doesn’t accept assignment?

A doctor who takes Medicare but doesn’t accept assignment can still treat Medicare patients but won’t always accept the Medicare-approved amount as payment in full.

This means they can charge you up to a maximum of 15 percent more than Medicare pays for the service you receive, called “balance billing.” In this case, you’re responsible for the additional charge, plus the regular 20 percent coinsurance, as your share of the cost.

How to cover the extra cost? If you have a Medicare supplement policy, better known as Medigap, it may cover the extra 15 percent, called Medicare Part B excess charges.

All Medigap policies cover Part B’s 20 percent coinsurance in full or in part. The F and G policies cover the 15 percent excess charges from doctors who don’t accept assignment, but Plan F is no longer available to new enrollees, only those eligible for Medicare before Jan. 1, 2020, even if they haven’t enrolled in Medicare yet. However, anyone who is enrolled in original Medicare can apply for Plan G.

Remember that Medigap policies only cover excess charges for doctors who accept Medicare but don’t accept assignment, and they won’t cover costs for doctors who opt out of Medicare entirely.

Good to know. A few states limit the amount of excess fees a doctor can charge Medicare patients. For example, Massachusetts and Ohio prohibit balance billing, requiring doctors who accept Medicare to take the Medicare-approved amount. New York limits excess charges to 5 percent over the Medicare-approved amount for most services, rather than 15 percent.

How do I find doctors who accept assignment?

Before you start working with a new doctor, ask whether he or she accepts assignment. About 98 percent of providers billing Medicare are participating providers, which means they accept assignment on all Medicare claims, according to KFF.

You can get help finding doctors and other providers in your area who accept assignment by zip code using Medicare’s Physician Compare tool.

Those who accept assignment have this note under the name: “Charges the Medicare-approved amount (so you pay less out of pocket).” However, not all doctors who accept assignment are accepting new Medicare patients.


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What does it mean if a doctor opts out of Medicare?

Doctors who opt out of Medicare can’t bill Medicare for services you receive. They also aren’t bound by Medicare’s limitations on charges.

In this case, you enter into a private contract with the provider and agree to pay the full bill. Be aware that neither Medicare nor your Medigap plan will reimburse you for these charges.

In 2023, only 1 percent of physicians who aren’t pediatricians opted out of the Medicare program, according to KFF. The percentage is larger for some specialties — 7.7 percent of psychiatrists and 4.2 percent of plastic and reconstructive surgeons have opted out of Medicare.

Keep in mind

These rules apply to original Medicare. Other factors determine costs if you choose to get coverage through a private Medicare Advantage plan. Most Medicare Advantage plans have provider networks, and they may charge more or not cover services from out-of-network providers.

Before choosing a Medicare Advantage plan, find out whether your chosen doctor or provider is covered and identify how much you’ll pay. You can use the Medicare Plan Finder to compare the Medicare Advantage plans and their out-of-pocket costs in your area.

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