What is Medicare assignment? It is an agreement between your healthcare provider and Medicare. The provider agrees to accept Medicare’s approved amount as full payment for a covered service. Under assignment, Medicare pays its share — typically 80% — and you pay only the remaining 20% coinsurance plus any applicable deductible.
No surprise charges. No extra billing beyond what Medicare approves. Roughly 98% of providers who bill Medicare are participating providers, meaning they accept assignment on every claim. In fact, approximately 99% of all Medicare claims are processed on assignment. Understanding how assignment works can save you hundreds or even thousands of dollars each year in unexpected medical costs.
How Does Medicare Assignment Actually Work?
Medicare divides providers into three categories based on their billing relationship with the program. Each category affects what you pay out of pocket.
Participating providers sign an annual agreement with CMS to accept assignment on every claim. They bill Medicare directly. You pay only the 20% coinsurance and your Part B deductible. In return, participating providers receive the full Medicare fee schedule rate. This arrangement gives you the most predictable costs.
Non-participating providers have not signed a participation agreement. They can decide whether to accept assignment on a claim-by-claim basis. Their reimbursement rate from Medicare is 5% lower than what participating providers receive. When they do not accept assignment, they may charge you more than the Medicare-approved amount. However, federal law caps that extra charge at 15% above their reduced fee schedule rate. This cap is called the limiting charge.
Opt-out providers have formally left the Medicare billing system entirely. They require you to sign a private contract. Medicare will not pay any portion of the bill. There is no cap on what they can charge. According to KFF research, roughly 1% of non-pediatric physicians have opted out of Medicare.
What Is Medicare Assignment’s Role in Protecting You from Excess Charges?
The financial protection that comes with assignment is substantial. When your provider accepts assignment, your cost for a covered service is limited to 20% of the Medicare-approved amount. That is a hard ceiling. The provider cannot send you an additional bill for the difference between their standard fee and Medicare’s rate.
Without assignment, you face what is known as balance billing. A non-participating provider can charge up to the limiting charge — 115% of the non-PAR fee schedule amount. Since that fee schedule is already 5% lower than the participating rate, the effective maximum comes to about 109.25% of the standard approved amount. The difference may seem small on one visit. Over multiple appointments, lab tests, and specialist referrals, those excess charges add up quickly.
Certain services require assignment by law, regardless of provider status. Clinical laboratory services must always be billed on assignment. Medicare pays nothing for lab work submitted without it. Durable medical equipment (DME) suppliers enrolled in Medicare must also accept assignment. Additionally, some states offer stronger protections. For example, Massachusetts and Ohio prohibit balance billing entirely for Medicare patients. New York caps excess charges at just 5% above the approved amount — well below the federal 15% limit.
How to Verify What Is Medicare Assignment Status for Your Providers
Checking your provider’s assignment status takes just a few minutes. The Medicare Care Compare tool on Medicare.gov lets you search for doctors, hospitals, and other providers. Each listing shows whether the provider accepts assignment. Look for the phrase “accepts Medicare-approved amount” in the results.
You can also call the provider’s billing office directly. Ask one simple question: “Do you accept Medicare assignment?” A participating provider will always say yes. A non-participating provider may accept assignment for some services but not others. Get the answer before your appointment — not after you receive the bill.
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Your State Health Insurance Assistance Program (SHIP) offers free, personalized counseling on Medicare billing issues. Trained SHIP counselors can help you understand excess charges, find participating providers in your area, and file complaints if a provider violates the limiting charge rule. Providers who exceed the limiting charge face penalties of up to $10,000 per violation, plus triple damages and possible exclusion from the Medicare program.
Frequently Asked Questions
Does accepting assignment mean the doctor works for free?
No. When a provider accepts assignment, Medicare pays 80% of the approved amount. You still owe the 20% coinsurance and any remaining Part B deductible. As a result, the provider receives full payment — just at Medicare’s approved rate rather than their own standard fee.
Can a doctor accept assignment for some visits but not others?
Yes, but only if they are a non-participating provider. Participating providers must accept assignment on every Medicare claim. Non-participating providers, however, can choose on a claim-by-claim basis. Typically, it is best to confirm assignment status before each appointment with a non-participating provider.
What is Medicare assignment’s connection to Medigap plans?
Some Medigap policies — specifically Plan F and Plan G — cover Part B excess charges. In most cases, these plans will pay the difference between the Medicare-approved amount and the limiting charge if your provider does not accept assignment. Still, choosing providers who accept assignment eliminates excess charges at the source, which is the most reliable protection.
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Official Sources & Resources
For verified information on Medicare regulations and consumer protection:
- Medicare.gov (Official Site): medicare.gov
- CMS (Centers for Medicare & Medicaid Services): cms.gov
- NAIC (National Association of Insurance Commissioners): naic.org
- KFF Medicare Research: kff.org/medicare
- Social Security Administration: ssa.gov
Content last reviewed June 2026. If you notice any outdated information, please contact us.