Medicare Assignment Explained: Participating, Non-Participating and Opt-Out Providers

What "accepting assignment" means

Medicare pays for a covered service based on a Medicare-approved amount. Medicare.gov explains on its page "Does your provider accept Medicare as full payment?" that when a doctor or other provider accepts the Medicare-approved amount as payment in full, this is called accepting assignment.

When your provider accepts assignment, Medicare.gov lists what that means for you:

• Your out-of-pocket costs may be lower.
• They agree to charge you only the Medicare deductible and coinsurance amount, and usually wait for Medicare to pay its share before asking you to pay yours.
• They have to submit your claim directly to Medicare and cannot charge you for submitting it.

What you pay when a provider accepts assignment

For most doctor services under Part B, Medicare.gov's Part B costs page says you pay 20% of the Medicare-approved amount after you meet the yearly Part B deductible, which is $283 in 2026. The deductible and premium change every year, so check that page for the current amounts. Medicare.gov's preventive services page notes that you pay nothing for most preventive services if the provider accepts assignment.

Participating, non-participating and opt-out providers

People often use "accepts Medicare", "accepts assignment" and "participates in Medicare" as if they were the same. They describe different arrangements.

Participating providers

CMS explains on its Medicare participation page that Medicare participation means the provider agrees to accept assignment on all claims for all Medicare-covered services furnished to their patients. You pay only the deductible and coinsurance, and the provider files the claim.

Non-participating providers

A non-participating provider is enrolled in Medicare but has not agreed to accept assignment on every claim. Medicare.gov says these providers may still accept the Medicare-approved amount on a case-by-case basis. According to the documentation of the CMS fee schedule tool, the Medicare payment amount for a non-participating physician is 95% of the amount for a participating physician.

When a non-participating provider does not accept assignment for your service, Medicare.gov says:

• You might have to pay the full amount at the time of service.
• They should still submit a claim to Medicare for covered services and cannot charge you for doing so. If they refuse, you can submit the claim yourself.
• They can charge you more than the Medicare-approved amount, but in many cases no more than 15% above it. This cap is called the limiting charge.

The CMS documentation explains that the limiting charge is set by law at 115% of the non-participating payment amount. Because that amount is already reduced to 95%, the limiting charge works out to 109.25% of what Medicare would pay a participating physician for the same service.

Opt-out providers

Some doctors and other providers opt out of Medicare. Medicare.gov explains that Medicare will not pay for items or services from a provider who opted out, except in emergencies. Providers opt out for a minimum of 2 years. If you choose to see an opt-out provider, you may need to pay upfront or set up a payment plan with the provider through a private contract. Outside emergencies, Medicare will not pay for any service from this provider, even a Medicare-covered one. Medicare.gov suggests talking to your State Health Insurance Assistance Program (SHIP) before signing a private contract.

Side-by-side comparison

How to check a provider before your visit

Ask the office

The simplest check is to ask: "Do you accept Medicare assignment for this service?" Ask about the specific service, since a non-participating provider decides claim by claim. If you have a Medicare Advantage plan instead of Original Medicare, ask whether the provider is in your plan's network, because the plan's own rules apply.

Medicare's own tools

Medicare's Care Compare tool lets you look up doctors and clinicians who work with Medicare. CMS publishes its doctor and clinician data as the Doctors and Clinicians National Downloadable File, and the data dictionary for that file defines an assignment indicator: "Y" means the clinician accepts the Medicare-approved amount as payment in full, and "M" means the clinician may accept Medicare assignment. For providers who opted out, CMS publishes the Opt Out Affidavits dataset, which lists each opt-out provider's NPI, specialty, address and effective dates.

What T-MedInfo shows

Clinician profiles on this site show the assignment indicator from the CMS Doctors and Clinicians file when the clinician is in that file:

• Accepts Assignment: the CMS value is "Y", the clinician accepts the Medicare-approved amount as payment in full.
• May Accept Assignment: the CMS value is "M", the clinician may accept Medicare assignment. Ask whether they will accept it for your service.
• Not Specified: the CMS file has no assignment value for the clinician.

City and specialty lists mark clinicians whose indicator is "Accepts Assignment". Clinicians who are not in the CMS file have no Medicare section on their profile. That does not mean they do not accept Medicare; they may simply not appear in the file.

We do not load the opt-out list, so a profile never says that a provider opted out. Use the CMS opt-out dataset for that.

The CMS file is a periodic snapshot. A clinician's arrangements can change, and the indicator describes the clinician, not every service or location. Always confirm with the office before a visit, especially for planned procedures.

Medicare Advantage and other coverage

Assignment, participation and the limiting charge are rules of Original Medicare. If you have a Medicare Advantage plan, Medicare.gov's plan comparison explains that costs, networks and referral rules are set by the plan, and out-of-network care may cost more or not be covered. The same page notes that Original Medicare has no yearly limit on what you pay out of pocket unless you have supplemental coverage, such as Medicare Supplement Insurance (Medigap), or other insurance, such as Medicaid or employer, retiree or union coverage.

Common questions

Can a provider who accepts Medicare still charge me more?

If they accept assignment for the service, they can charge only the deductible and coinsurance for covered services. They can charge more if they are non-participating and do not accept assignment for that service, within the limiting charge where it applies, or if the service is not covered by Medicare.

Is the 20% based on the doctor's bill?

No. Coinsurance is based on the Medicare-approved amount, which is often lower than the charge the office submits. Our Part B pricing guide explains submitted charges and allowed amounts.

Does "May Accept Assignment" mean I will pay more?

Not necessarily. It means the clinician can decide per claim. Ask before the visit whether they will accept assignment for your service.