Under Original Medicare, doctors and suppliers who accept Medicare choose how they enroll. Participating providers accept assignment (Medicare’s approved amount). Non-participating providers may charge you a limited amount above the Medicare-approved amount on Part B services—that extra slice is often called a Part B excess charge. Some Medigap letters help with excess charges; Medicare Advantage uses different network and MOOP rules instead.
This page is excess charges on Original Medicare Part B—not IRMAA premiums (Medicare IRMAA basics) or late-enrollment penalties (Medicare late enrollment penalty basics).
Participating vs non-participating (orientation)
| Provider status | What you typically pay beyond Part B deductible / coinsurance |
|---|---|
| Participating (accepts assignment) | Your usual Part B deductible and 20% coinsurance on the approved amount; no excess charge |
| Non-participating, still treats Medicare patients | May bill you up to the limiting charge (commonly described as 15% over the non-participating approved amount)—that extra is the excess charge |
| Opt-out / private contract | Different rules; Medicare usually does not pay; excess-charge Medigap benefits generally do not apply the same way |
Not every state allows excess charges the same way—some states limit or ban them for physicians. Use Medicare.gov’s physician compare tools and your state SHIP program to check a specific doctor. Deductible vocabulary still helps: Health insurance deductibles.
How Medigap interacts
Standardized Medigap letters differ on excess charges:
- Letters that include Part B excess-charge coverage (commonly Plan F where still available to eligible people, and Plan G in most states) can pay that limiting-charge slice after Medicare processes the claim.
- Letters that omit excess-charge coverage (for example Plan N in the usual chart) leave you responsible for excess charges if a non-participating provider bills them.
- Exact letter charts are state- and cohort-specific (Plan F is generally closed to newly eligible people). Read the insurer’s outline of coverage from carriers such as UnitedHealthcare, Humana, Mutual of Omaha, or regional Blues.
Medigap does not erase medical bill fights over coding errors, noncovered services, or balance bills outside Medicare rules.
Worked example: $1,000 approved outpatient service
Alex has Original Medicare and has already met the Part B deductible for the year. A non-participating specialist’s Medicare-approved amount for an outpatient procedure is $1,000 (illustrative). Rough coinsurance math people use for orientation:
| Slice | Illustrative amount |
|---|---|
| Medicare Part B pays ~80% of the relevant approved figure | ~$800 region (exact non-par approved math is set by CMS tables) |
| Alex’s standard 20% coinsurance slice | ~$200 region |
| Possible excess charge up to limiting charge | Up to roughly 15% over the non-participating approved amount—often cited around $150 on a $1,000 example before state limits |
- With a Medigap letter that covers excess charges (e.g., Plan G): after Medicare processes the claim, the supplement may cover the excess-charge slice per the policy; Alex still owes the Part B deductible (if not met) and the Medigap premium.
- With a letter that skips excess charges (e.g., Plan N): Alex may owe the excess-charge amount in addition to plan-specific copays.
- On Medicare Advantage: Alex follows that plan’s network and MOOP rules instead; Medigap generally cannot be paired with Advantage.
Always use the remittance / Medicare Summary Notice numbers—not a blog table—for your bill.
Practical habits
- Ask every specialist’s office: “Do you accept Medicare assignment?”
- Prefer participating providers when you want to avoid excess-charge risk.
- If you keep a Medigap letter without excess-charge coverage, budget for limiting charges or switch providers.
- Compare Medigap premiums for the same letter; benefits are standardized in most states, prices are not.
- Keep Medicare Summary Notices; dispute coding mistakes promptly.
- Do not confuse excess charges with IRMAA or late-enrollment premium add-ons.
Checklist
- Confirm you are on Original Medicare (A + B), not Advantage, before applying excess-charge rules.
- Check whether each key doctor participates and accepts assignment.
- Read your Medigap outline for Part B excess charges yes/no.
- In limited-charge states, confirm local physician billing rules via SHIP.
- Save MSNs and itemized bills for any surprise balance.
- Re-shop providers before elective procedures if excess charges are a pattern.
Shop Medigap letters during the guaranteed-issue open enrollment window when you can: Medigap open enrollment basics.
Annual Part B deductible before coinsurance and Medigap fill-ins: Medicare Part B deductible basics.
Choosing Medigap letters when a guaranteed-issue right applies: Medigap guaranteed issue basics.
Educational only. Not insurance, tax, or legal advice. Not a plan recommendation. Medicare assignment rules, limiting charges, state bans, and Medigap letter benefits change; confirm with Medicare.gov, your state SHIP program, and insurer outlines of coverage.