Most doctors accept Medicare as full payment for their services. But some accept it only for certain services, and others don’t accept it at all.

What does this mean for you?

If you have Original Medicare, it means you should try to use doctors, hospitals, medical equipment suppliers, and other healthcare providers that participate or “accept assignment” in Medicare. Such providers have signed agreements to take Medicare as payment in full for their services.

If your doctor or other provider accepts assignment:

Your out-of-pocket costs may be less.

The provider agrees to charge you only the Medicare deductible and coinsurance amount, and usually waits for Medicare to pay its share before asking you to pay your share.

The provider has to submit your claim directly to Medicare and can’t charge you for submitting the claim.

Some doctors and other providers haven’t signed an agreement to accept assignment for all Medicare-covered services, but they can still choose to accept assignment for some services. These providers are called “non-participating” providers.

If your doctor or other provider doesn’t accept assignment:

You may have to pay the entire bill at the time of service. Your provider is supposed to submit a claim to Medicare for any Medicare-covered services they provide to you.

The provider can’t charge you for submitting a claim. If they don’t submit the Medicare claim once you ask them to, call 1-800-MEDICARE.

In some cases, you might have to submit your own claim to Medicare using Form CMS-1490S to get paid back.

The provider can charge you more than the Medicare-approved amount, but there’s a limit. Non-participating providers are paid 95% of the Medicare-approved amount. They can only charge you up to 15% over the amount that non-participating providers are paid.

The 15 percent limit applies only to certain Medicare-covered services and doesn’t apply to some medical supplies and durable medical equipment.

Some doctors and other providers don’t want to enroll in the Medicare program at all. You can still visit these “opt out” providers, but they must enter into a private contract with you (unless you’re in need of emergency or urgently needed care).

A private contract is a written agreement between you and a doctor or other provider who has decided not to provide services to anyone through Medicare. The private contract only applies to services you get from the provider who asked you to sign it.

If you sign a private contract with an opt-out doctor or other provider, keep in mind that Medicare won’t pay any amount for the services you get from that provider, even Medicare-covered services.

You’ll have to pay the full amount this provider charges you. You and your provider will set up your own payment terms through the contract.

If you have a Medicare Supplement Insurance (Medigap) policy, it won’t pay anything for the services you get. Call your insurance company before you get the service if you have questions.

Your provider must tell you if Medicare would pay for the service if you got it from another provider who accepts Medicare.

Your provider must tell you if he or she has been excluded from Medicare.

You can’t be asked to sign a private contract for emergency or urgent care.

You’re always free to get services not covered by Medicare if you choose to pay for them yourself.

You don’t have to sign a private contract. You can always go to another provider who participates (accepts assignment) in Medicare.

Be sure to ask your physician or other provider if they are participating, non-participating, or opt-out. You can also check by calling 1-800-MEDICARE or by using Medicare’s Physician Compare tool on www.medicare.gov.

You may want to contact your State Health Insurance Assistance Program (SHIP) to get free help before signing a private contract with any doctor or other health care provider.

Greg Dill is Medicare’s regional administrator for Arizona, California, Nevada, Hawaii, and the Pacific Territories. You can always get answers to your Medicare questions by calling 1-800-MEDICARE (1-800-633-4227).