The difference between Medicare participating and non-participating providers comes down to what they can charge you. A participating provider has signed a yearly agreement to accept Medicare’s approved amount as full payment, so you pay only your Part B deductible and 20% coinsurance. A non-participating provider has not signed that agreement and can bill up to 15% above a reduced approved amount, which shifts more of the cost onto you and often requires you to pay the full bill upfront while you wait for Medicare to reimburse you. Both categories still see Medicare patients. The rules that follow apply to Original Medicare Part B; Medicare Advantage plans run their own networks with separate terms.
What a Participating Provider Agrees To
A participating provider signs an annual agreement with Medicare to accept “assignment” on every claim for every Medicare patient.1Social Security Administration. Social Security Act 1842 – Payment of Benefits Assignment means the provider treats Medicare’s approved amount as the total price and cannot bill you more than your share of it.
Your share is predictable. You pay the annual Part B deductible ($283 in 2026) and then 20% coinsurance on covered services.2Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles The provider collects 80% of the approved amount straight from Medicare, files the paperwork, and bills you only for the remaining 20%. If Medicare approves $200 for a procedure, you owe $40. Nothing extra can be added on top.
What a Non-Participating Provider Can Charge
Providers who skip the annual participation agreement can still see Medicare patients, but they haven’t committed to accepting assignment on every claim. They decide claim by claim. In exchange for that flexibility, Medicare cuts their approved amount by 5% compared to what a participating provider receives.3Social Security Administration. Social Security Act 1848 – Payment for Physicians Services
Federal law then caps their price through a “limiting charge” set at 115% of that reduced approved amount.3Social Security Administration. Social Security Act 1848 – Payment for Physicians Services Compare the same $200 service side by side:
- At a participating provider, Medicare approves $200. Medicare pays $160. You pay $40. Total: $200.
- At a non-participating provider, the approved amount drops 5% to $190. The limiting charge is 115% of $190, or $218.50. You pay the office $218.50 up front, and Medicare mails you back 80% of $190, which is $152. Net cost to you: $66.50.
The same service costs $40 at the first office and $66.50 at the second. On expensive procedures, or across many visits in a year, the gap compounds fast.
Services Where Assignment Is Always Required
Some services must be billed on assignment no matter what the provider’s general status is. On these, you pay only the standard deductible and 20% coinsurance even from a non-participating provider, because the limiting charge doesn’t apply:
- Clinical laboratory tests, including blood work
- Ambulance services
- Drugs and biologicals administered in a clinical setting
- Any service provided to a patient who qualifies for both Medicare and Medicaid
Separately, some providers formally opt out of Medicare altogether and bill through private contracts with no federal price cap. That is a different category from non-participating and is worth confirming if a provider tells you they don’t take Medicare at all.
How Payment Flows at Each Type of Office
Where the money moves depends on whether the provider accepts assignment for that particular visit.
When assignment is accepted, the office files the claim, receives 80% directly from Medicare, and bills you for the 20% coinsurance. You never front the full cost, and the paperwork is handled for you.
When a non-participating provider does not accept assignment, the office can ask you to pay the entire bill (up to the limiting charge) before you leave. The provider is still legally required to submit the claim to Medicare on your behalf.3Social Security Administration. Social Security Act 1848 – Payment for Physicians Services Medicare then processes the claim and mails a reimbursement check to you, not to the office, for 80% of the non-participating approved amount. You need enough cash or credit on hand to cover the full bill and enough patience to wait weeks for the check.
How Medigap Plans Treat Excess Charges
The extra amount a non-participating provider bills above Medicare’s approved figure is called an “excess charge,” and only some Medigap policies cover it. Medicare Supplement Plans F and G pay 100% of Part B excess charges.4Medicare.gov. Compare Medigap Plan Benefits With either plan, your insurer picks up the excess and you owe only standard coinsurance.
Plan N does not cover excess charges.4Medicare.gov. Compare Medigap Plan Benefits If you carry Plan N and see a non-participating provider who bills the maximum, that difference is yours to absorb. This detail rarely matters until the bill lands. If your doctors are mostly participating providers, Plan N’s lower premium may still be the better deal. If you routinely see non-participating specialists, Plan F or G tends to pay for itself.
States That Ban Excess Charges
About eight states have laws that prohibit non-participating providers from billing any excess charge above Medicare’s approved amount. In those states, a non-participating provider has to accept the approved amount as full payment, which effectively erases the limiting charge for care delivered within state lines. The protection is tied to where the service is provided, so crossing state lines for an appointment can change the rules that apply to your bill. Your state insurance department or local State Health Insurance Assistance Program (SHIP) can tell you whether your state is on that list.
How to Check a Provider’s Status Before You Book
The Medicare Care Compare tool at medicare.gov lets you search by name, specialty, or location and shows whether a provider participates in Medicare.5Medicare.gov. About Medicare Care Compare The database may lag recent changes in status, so a phone call to the office is still worth making, especially with a new specialist.
Ask two specific questions when you call:
- Are you a participating Medicare provider?
- Will you accept assignment for the service I’m scheduled for?
A non-participating provider may accept assignment on one visit and not the next, so the answer can vary by procedure. Getting it in writing, or at least noted before the appointment, is what keeps you from being handed a full-price bill at checkout with a reimbursement check somewhere down the road.