Medicare Supplement Plan N: What It Covers and What It Doesn't

What This Means

You have Medigap Plan N, which covers most of what Original Medicare doesn’t — but not everything. If you received a bill after a doctor or emergency room visit, it may not be a mistake. Plan N is designed to leave a few specific costs in your hands: small copays on certain office and ER visits, and something called Part B excess charges, which are the extra fees some doctors charge above what Medicare has approved. This guide explains what Plan N covers, what it deliberately leaves out, and how to tell the difference between a built-in cost and a billing or crossover error.

Why This Happens

• Plan N includes copays for some visits by design. Plan N pays 100% of your Part B coinsurance, but you may owe a copay of up to $20 for some office visits and up to $50 for an emergency room visit that doesn’t result in inpatient admission. These are part of the plan’s structure, not mistakes.
• Plan N does not cover Part B excess charges. If your doctor doesn’t accept Medicare assignment — meaning they haven’t agreed to accept the Medicare-approved rate as payment in full — they can legally charge up to 15% more than that rate for most services (the limiting charge, 42 CFR 414.48). Plan N does not cover this difference; you pay it out of pocket.
• An opt-out doctor is a different situation from a non-participating one. A small number of doctors have formally opted out of Medicare and signed a private contract with each patient (42 CFR 405.415) — with a valid contract, Medicare’s payment limits don’t apply and neither Medicare nor Plan N pays anything toward the visit. There’s an exception for emergency or urgent care without a signed contract: the doctor must bill Medicare and can collect no more than the limiting charge; Medicare processes that claim, so Plan N pays its usual share — you owe at most the Plan N copay, any unmet Part B deductible, and any excess up to the limiting charge (42 CFR 405.440). A non-physician practitioner who opted out (nurse practitioner, physician assistant, psychologist, clinical social worker and similar) can collect only your deductible and coinsurance (42 CFR 405.440(b)(2)(ii)) — so with Plan N you’d owe only the copay and any unmet deductible, with no excess charge.
• A provider who accepts Medicare assignment can’t charge you more than the Medicare-approved amount. If a provider who accepted assignment on the claim billed you above that amount, that’s a provider billing error, not a Plan N coverage gap — ask the provider’s billing office for a corrected bill and don’t pay the extra.
• Medicare may not have finished crossing the claim over to your insurer yet. Medicare is supposed to automatically forward your claim to your Medigap insurer through an electronic system called the Coordination of Benefits Agreement (COBA) crossover process. If that transfer is delayed or fails, your bill may look like Plan N didn’t pay when the claim simply hasn’t reached your insurer yet — or never reached it, and needs to be resubmitted.
• The service may have been coded in a way that affects Plan N’s payment. A billing code that looks routine to you may trigger a different coverage rule. If the amount you owe doesn’t match what your Plan N policy says, a coding issue could be the cause.
• You may not have met the Part B deductible yet. Plan N does not cover the annual Part B deductible ($283 in 2026). Early in the year, some or all of a service cost may be applied to that deductible before Plan N pays anything.

Should You Appeal?

What To Do Next

1. Review your MSN and Plan N EOB side by side. Your MSN shows what Medicare approved and paid. Your Plan N EOB shows what your Medigap insurer paid and what it says is your responsibility. If both documents agree on what you owe, it is likely correct. If they conflict, there may be a processing or billing problem. If your Medigap insurer says it never received the claim, see our guide to Medigap crossover problems.
2. Request an itemized bill from your provider. Ask for a line-by-line statement showing each service, its billing code, and the charge. Compare it against your MSN to make sure the services billed are the ones you actually received.
3. Check whether your doctor accepts Medicare assignment, and whether they’ve opted out entirely. You can search providers at Medicare.gov’s Care Compare tool, though it won’t tell you whether a doctor has opted out — CMS’s opt-out lookup tool does: Provider Opt-Out Affidavits Look-Up Tool. A “non-participating” provider can charge up to the 15% limiting charge, which Plan N doesn’t cover; a provider who accepts assignment can’t charge more than the Medicare-approved amount. An “opt-out” doctor must have given you a written private contract to sign before treating you (42 CFR 405.415). With a valid contract, Medicare’s payment limits don’t apply, Medicare pays nothing toward the visit, and Plan N pays nothing either, because Medigap only supplements what Medicare itself would have covered. If you never signed one and it wasn’t emergency or urgent care, the provider broke the opt-out rules. A doctor can then collect no more than the limiting charge, and a non-physician practitioner (nurse practitioner, physician assistant, psychologist, clinical social worker and similar) only your deductible and coinsurance (42 CFR 405.435(b)(5), (7)). Refunding anything above that is how the rules expect them to put it right (405.435(d)) — ask for the refund, and report it to 1-800-MEDICARE. Medicare generally still won’t pay the claim (a narrow exception covers care within 15 days of the opt-out notice, if you file the claim yourself — 405.435(c)), so Plan N generally won’t either.
4. Confirm the Part B deductible status. Check your MSN to see how much of the current year’s deductible you’ve already met. If the bill was applied to your deductible, that is not a Plan N failure — it’s how the benefit is structured.
5. Contact your Plan N insurer if the amounts don’t add up, or if the claim never crossed over. Call member services and ask specifically whether the claim crossed over from Medicare through the COBA process. If it didn’t, ask the insurer to request the claim from Medicare, or have your provider send it to the insurer directly with the Medicare claim number from your MSN — see our guide to Medigap crossover problems. If it did and the insurer paid less than your Plan N policy says it should, that’s a dispute to raise with the insurer directly — and with your state insurance department or SHIP if the insurer doesn’t resolve it.
6. File a redetermination if you believe Medicare itself processed something incorrectly — for example, whether your deductible was met, how your coinsurance was computed, or whether a service was covered at all. A redetermination is Medicare’s first level of formal appeal and must be filed within 120 days of the date you receive your MSN, presumed to be 5 days after the date on it (42 CFR 405.942(a)(1)). File it in writing, using form CMS-20027 or following the instructions on your MSN, which also shows your deadline.
7. If you’d like help reviewing your bill or identifying whether a charge looks like a billing error, Barley can do a free bill analysis. Check My Bill for Free.

Sources

• Medicare.gov: Compare Medigap plan benefits — official comparison of what each Medigap plan letter covers, including Plan N’s $20/$50 copays and its Part B excess-charge exclusion.
• Medicare.gov: What’s Medicare Supplement Insurance (Medigap)? — overview of how Medigap supplements Original Medicare.
• Medicare.gov: “Medicare Summary Notice” (MSN) — what the MSN shows and how to use it to check a claim, including the appeal instructions on its last page.
• CMS: Coordination of Benefits (COBA) overview — how Medicare’s crossover process forwards claims to Medigap and other secondary payers.
• CMS: 2026 Medicare Parts A & B Premiums and Deductibles — current Part B deductible amount, which Plan N does not cover.
• 42 CFR 405.415: Private contracts (opt-out providers) — what an opt-out contract requires, and that Medigap plans do not pay for opt-out services.
• 42 CFR 405.440: Emergency and urgent care services — the exception that lets an opt-out doctor bill Medicare, and collect no more than the limiting charge, for emergency or urgent care when no prior private contract exists.
• 42 CFR 405.435: Failure to maintain opt-out — a doctor who bills a patient without a signed private contract (outside the emergency/urgent-care exception) is subject to the limiting charge (405.435(b)(5)), a non-physician practitioner may collect only the deductible and coinsurance (405.435(b)(7)), amounts above that must be refunded (405.435(d)), and a narrow exception lets the beneficiary file the claim within 15 days of the opt-out notice (405.435(c)).
• 42 CFR 414.48: Limiting charge — 115% of the non-participating fee-schedule amount — 15% above the Medicare-approved amount on your MSN (42 CFR 414.48(b)).
• Medicare.gov: Does your provider accept Medicare as full payment? — providers who accept assignment agree to charge only the Medicare-approved amount.
• 42 CFR 405.942: Redetermination filing deadline — the 120-day window, running from presumed receipt of the notice.
• 42 CFR 405.924: Redetermination — issues reviewed — whether a service was covered, deductible met, and coinsurance computation as reviewable issues.
• CMS: First Level of Appeal (Redetermination by a Medicare Contractor) — a redetermination must be requested in writing, using form CMS-20027 or a written request.
• Medicare.gov: Talk to Someone — filing a complaint through your State Health Insurance Assistance Program (SHIP) when a plan issue isn’t resolved.

Frequently Asked Questions