Medicare beneficiaries who see a doctor outside the program’s standard payment agreement can be billed up to 15 percent more than the approved rate for Part B services. That extra charge is not a billing error or a surprise fee. It is a federally authorized surcharge, set by statute at 115 percent of the Medicare Physician Fee Schedule amount, and it applies every time a nonparticipating provider treats a Medicare patient without accepting assignment. For millions of older Americans on fixed incomes, the difference between a participating and nonparticipating doctor can mean real money out of pocket, visit after visit.
How the 115 percent limiting charge works in practice
The legal architecture behind this billing gap is specific. Under federal regulation, a nonparticipating supplier who does not accept assignment may charge a beneficiary up to 115 percent of the fee schedule amount for items and services paid under the Physician Fee Schedule. That 15 percent ceiling is the “limiting charge,” and it caps what nonparticipating doctors can bill above Medicare’s approved rate.
The distinction between participating and nonparticipating providers matters because it determines who absorbs the cost gap. Participating physicians sign an agreement with Medicare to accept the program’s approved amount as full payment for covered services, a framework explained in CMS guidance on provider participation. Nonparticipating physicians do not make that blanket agreement, and the limiting charge gives them room to bill patients directly for the difference between Medicare’s allowed amount and their higher charge.
A separate legal track exists for physicians who opt out of Medicare entirely through private contracts governed by 42 U.S.C. 1395a. When a physician opts out under this statute, the 115 percent cap no longer applies, Medicare does not pay for the services, and the full cost is determined by the private agreement between doctor and patient. Beneficiaries who sign these contracts are responsible for the entire bill, with no reimbursement from traditional Medicare.
The practical result is a three-tier system. A participating doctor bills Medicare, accepts its rate as payment in full (minus the beneficiary’s deductible and coinsurance), and cannot tack on an excess charge. A nonparticipating doctor may choose on a claim-by-claim basis whether to accept assignment; when they do not, they can charge up to 115 percent of the fee schedule amount, and the patient owes the difference. An opted-out doctor can charge whatever the patient agrees to pay in the private contract, with no Medicare payment at all. Most beneficiaries who encounter higher bills fall into the middle tier, where the limiting charge creates a predictable but often overlooked out-of-pocket cost.
Regional reimbursement gaps and who pays the most
The 115 percent cap applies uniformly across the country, but the dollar impact varies because Medicare’s fee schedule itself differs by region. Geographic practice cost indices adjust the Physician Fee Schedule so that approved amounts for the same procedure can be lower in some rural areas and parts of the South than in high-cost metropolitan regions. When a nonparticipating physician in a lower-reimbursement area bills the full limiting charge, the 15 percent surcharge sits on top of an already reduced base rate. Even though the percentage is the same, the combination of lower approved fees and repeated visits can create a meaningful strain on household budgets.
In communities with few specialists, beneficiaries may have little choice but to see a nonparticipating doctor if they want timely care close to home. That can mean paying the limiting charge for every office visit, diagnostic test, or minor procedure, especially in practices that routinely decline assignment. Over the course of a year, those incremental excess charges can add up to hundreds of dollars in additional costs for people living on Social Security or modest retirement savings.
Some Medigap policies cover Part B excess charges, but not all. The official Medigap comparison shows that only certain standardized plans include this benefit, while others pay only the standard 20 percent coinsurance and leave excess charges to the beneficiary. People who chose a supplement without excess-charge coverage, or who enrolled in Medicare Advantage instead of traditional Medicare plus a Medigap policy, have no dedicated buffer against the limiting charge. For them, the decision to see a nonparticipating doctor translates directly into higher out-of-pocket costs.
The gap between plan types becomes a practical financial question every time a beneficiary schedules care. Someone with a Medigap plan that pays excess charges may be largely insulated from the 115 percent rule and can focus on other factors, such as provider quality and convenience. By contrast, a person with no such protection may need to call ahead to confirm a doctor’s participation status, ask whether the practice accepts assignment, and weigh the cost of potential excess charges against the burden of traveling farther to see a participating provider.
Consumer advocates often urge beneficiaries to check a doctor’s Medicare participation status before establishing care, and to revisit that choice if bills begin to include unexplained balances above the usual 20 percent coinsurance. While the limiting charge is legal and capped, it is also optional from the patient’s perspective: in many areas, another physician or clinic will accept assignment and eliminate the surcharge. Understanding how the 115 percent rule operates, and how Medigap coverage interacts with it, can help older adults avoid avoidable costs and stretch their Medicare benefits further.
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