Most Medigap plans leave some costs for you to pay. The most common reasons are the Part B deductible ($283 in 2026), which Plan G and most other plans sold today don't cover, copays under Plan N, the 50% or 75% cost sharing in Plans K and L, and excess charges from doctors who don't accept Medicare assignment. You may also get a bill when Medicare denies a service, or when the provider bills you before your Medigap plan has paid.
Does Medigap pay everything Medicare doesn't?
It depends on your plan letter. Medicare's "Choosing a Medigap Policy" guide shows that each standardized plan covers a different mix of costs. Some plans are designed to leave certain costs to you.
Find your plan letter on your card or policy, then check the reasons below.
Reason 1: The Part B deductible
The 2026 Part B deductible is $283, according to CMS. Medicare's guide says Medigap plans sold to people new to Medicare on or after January 1, 2020, can't cover it. In the 2026 chart, only Plans C and F cover the Part B deductible, and those aren't available to people new to Medicare since that date.
So if you have Plan G, D, N, or most others, expect to pay the first $283 of Medicare-approved Part B costs each year yourself. Those bills usually come early in the year.
Reason 2: Plan N copays
Plan N pays the Part B coinsurance except for a copayment of up to $20 for some office visits and up to $50 for emergency room visits that don't result in an inpatient admission, per Medicare's guide. Those small bills from doctor's offices are expected with Plan N.
Reason 3: Plans K and L share costs
Plans K and L pay a percentage of many benefits. In the 2026 chart, Plan K pays 50% and Plan L pays 75% of the Part B coinsurance, among other items. You pay the rest until you reach the plan's yearly out-of-pocket limit and your Part B deductible. After that, the plan pays 100% of covered services for the rest of the year.
Reason 4: Excess charges
If a doctor doesn't accept Medicare assignment, Medicare.gov says they can charge more than the Medicare-approved amount, in many cases up to 15% more. Medicare's guide calls this an excess charge. In the 2026 chart, only Plans F and G cover Part B excess charges. With any other plan, that extra is yours to pay.
To avoid it, ask before your visit: "Do you accept Medicare assignment?"
Reason 5: A high-deductible plan
Some states offer high-deductible versions of Plans F and G. Medicare's guide says you pay Medicare-covered costs up to $2,950 in 2026 before the policy pays anything. Until you reach that amount, bills come to you.
Reason 6: Medicare denied the service
Medigap pays its share after Medicare pays its share of an approved amount. If Medicare denies a service, your Medigap plan generally doesn't pay either. Check your Medicare Summary Notice (MSN) for "NO" in the "Service approved?" column.
If you signed an Advance Beneficiary Notice of Noncoverage (ABN), Form CMS-R-131, before the service, the Centers for Medicare & Medicaid Services (CMS) says that form shifts potential financial responsibility to you when Medicare is expected to deny payment. You can still appeal a denial if you chose the option asking the provider to bill Medicare.