Medicare Part B Excess Charges: The Real Math Behind the “15%” a Non-Participating Provider Can Bill

By YourResourceHub Editorial Team · Reviewed by Steven Sun · 8 min read · Last updated September 15, 2026

A non-participating Medicare provider can legally bill up to a federal “limiting charge” equal to about 109.25% of the Medicare-approved amount for a Part B service. Medigap Plans F and G cover that excess amount in full; every other standardized Medigap plan does not. A handful of states restrict or ban the practice outright, though the real list is narrower than what commonly circulates online.

In this article

• What a Medicare Part B excess charge actually is
• Who is exposed, and who has some protection
• The exact math behind the “15%” limiting charge
• How to protect yourself before the bill arrives
• What seniors get wrong about excess charges
• Frequently asked questions

Harold Vance, 71, saw a specialist for a follow-up his primary care doctor had referred him to. Medicare approved $100 for the visit. The specialist didn’t accept assignment, and the bill that arrived a few weeks later was $109.25, nine dollars and twenty-five cents more than Medicare’s approved amount. Harold’s Medigap Plan N didn’t cover a cent of the difference.

What a Medicare Part B excess charge actually is

Medicare classifies every doctor and supplier three ways. A participating provider accepts the Medicare-approved amount as full payment for every Medicare-covered service, an arrangement called “accepting assignment.” A non-participating provider is still enrolled in Medicare but decides case by case whether to accept assignment, and can charge more when they don’t, per Medicare’s own explanation. A provider who has fully opted out of Medicare doesn’t bill Medicare at all; the patient and provider sign a private contract instead, Medicare pays nothing, and none of the limits below apply to that visit.

An excess charge, also called a Part B excess charge, is the amount a non-participating provider bills above what Medicare approved, on a Part B-covered service where the provider didn’t accept assignment.

Who is exposed, and who has some protection

Excess charges apply narrowly. Medicare’s rule caps a non-participating provider’s bill at a federal limiting charge, and the cap does not apply to durable medical equipment or supplies, only to certain Part B services. It also doesn’t apply at all if the provider has opted out of Medicare entirely, since an opted-out provider isn’t billing Medicare under any of these rules in the first place.

Two things reduce exposure further. First, participating providers are the overwhelming norm: 98% of physicians and practitioners who billed Medicare in 2022 were participating, according to KFF (formerly the Kaiser Family Foundation), which analyzed enrollment data from the Centers for Medicare & Medicaid Services (CMS). About 1.2% of non-pediatric physicians (concentrated heavily in psychiatry) were fully opted out of Medicare as of late 2024.

Second, a Medigap policy can absorb the excess charge, but only two of the ten standardized plan types do. Per Medicare’s own plan comparison chart, Plans F and G cover Part B excess charges at 100%. Plans A, B, C, D, K, L, M, and N do not; someone enrolled in one of those, including Harold with his Plan N above, is responsible for the excess amount out of pocket. Plan F is no longer available to anyone who became eligible for Medicare on or after January 1, 2020; Plan G carries the same standardized benefits as Plan F except for the Part B deductible, and is the closest equivalent available to someone newly eligible today. See our guide to Medigap vs. Medicare Advantage open enrollment windows for how these enrollment rules fit together, and our guide to Medicare Savings Programs if the concern is affording any coverage at all rather than an occasional excess charge.

State law adds a third layer, and this is where a lot of consumer content gets sloppy. A commonly repeated list names eight states as banning excess charges outright. Checking each one against its own state government source tells a messier story:

State	What the law actually does
Massachusetts	Broad ban – physicians treating Medicare patients agree not to charge more than the government-determined reasonable charge
Ohio	Broad ban on balance billing a Medicare beneficiary above the approved amount
Pennsylvania	Broad ban under a dedicated state Medicare fee-control law
Minnesota	Ban applies to Minnesota residents only; an out-of-state patient treated in Minnesota is not covered
Rhode Island	Ban enforced through professional licensing discipline rather than a price cap
Vermont	Ban on the books, but ordinary office and home visits are specifically excepted from it, the exact visit type this article’s own example covers
New York	Caps most services at 5% over the approved amount, but the state’s own fact sheet excludes office and home evaluation visits from that cap – those revert to the federal 15% limiting charge, the same category as Harold’s specialist visit
Connecticut	Not a ban – the state’s own Medicare counseling program confirms only the lowest-income enrollees, those in the Qualified Medicare Beneficiary (QMB) program, are protected

The exact math behind the “15%” limiting charge

Medicare’s consumer materials describe the limiting charge as 15% above the Medicare-approved amount, and that’s a close but not exact shorthand for a two-step calculation set out in federal regulation. Here’s the actual mechanic, worked on a $100 Medicare-approved amount:

1. Medicare first sets a separate, lower fee schedule amount for non-participating providers, equal to 95% of the participating amount. On a $100 approved amount, that’s $95.
2. The limiting charge is 115% of that $95 non-participating amount, not 115% of the original $100. That’s $95 multiplied by 1.15, which equals $109.25.

So the true limiting charge works out to about 109.25% of the original Medicare-approved amount, not a flat 115%. On Harold’s $100 approved visit, $109.25 is the most the specialist could legally bill him, and that’s exactly what showed up on his statement.

How to protect yourself before the bill arrives

Ask directly whether a provider accepts Medicare assignment before you’re billed, not after. A participating provider’s office should be able to answer immediately; if a scheduler says the doctor is “non-participating” or “doesn’t take assignment,” expect a bill above the approved amount unless your state restricts it or your Medigap plan is Plan F or Plan G.

Check your own Medigap plan letter against Medicare’s plan comparison chart if you’re enrolled in one. If you’re weighing Medigap options during an enrollment window and excess-charge protection matters to you, that’s one factor to weigh against each standardized plan’s full benefit chart and your own state’s rules, not a reason to assume any single insurer’s version of a plan changes what the standardized benefits cover.

If a bill looks wrong, ask the provider’s billing office for the claim’s Medicare-approved amount in writing and check the math above before you pay it.

What seniors get wrong about excess charges

The most common mistake is assuming every Medigap plan covers this. Only Plans F and G do. Someone on Plan N, like Harold, or on a Medicare Advantage plan with different cost-sharing rules entirely, can still owe the difference.

The second mistake is trusting a flat state-by-state list found online without checking the actual statute. As the table above shows, three commonly cited “ban” states, Vermont, New York, and Connecticut, don’t actually eliminate the charge for an ordinary office visit like Harold’s. Confirm your own state’s rule with your State Health Insurance Assistance Program counselor rather than trusting an unsourced list; our guide to the Medicare Annual Wellness Visit covers a related billing mix-up worth knowing about before your next appointment.

Frequently asked questions

What is a Medicare Part B excess charge? It’s the amount a non-participating Medicare provider bills above the Medicare-approved amount for a Part B service. Federal rules cap it at a limiting charge equal to roughly 109.25% of the approved amount, commonly described as about 15% over.

Does my Medigap plan cover excess charges? Only Medigap Plans F and G cover Part B excess charges at 100%, per Medicare’s own standardized benefit chart. Plans A, B, C, D, K, L, M, and N do not, so you’d owe the excess amount yourself under any of those.

Which states ban excess charges? Massachusetts, Ohio, and Pennsylvania restrict it broadly. Minnesota’s protection covers residents only. Vermont’s ban and New York’s 5% cap both specifically exclude ordinary office and home visits, reverting those to the federal 15% limiting charge, and Connecticut protects only its lowest-income enrollees, not everyone on Medicare.

How do I know if my doctor is a participating provider? Ask the billing office directly before your appointment whether they accept Medicare assignment. About 98% of physicians who billed Medicare in 2022 were participating, so most visits carry no excess-charge risk at all.

Can a provider who opted out of Medicare bill me anything they want? Yes, within a private contract you sign directly with that provider. Medicare pays nothing toward that visit, and none of the limiting-charge rules described here apply, since the visit isn’t billed to Medicare at all.