A Medicare cost plan is not a Medicare Advantage plan. It is a different kind of contract, authorised under section 1876 of the Social Security Act, and it behaves differently in one respect that matters more than all the others: a member who goes outside the plan can fall back on Original Medicare for that care.
The fallback rule
Under a Medicare Advantage plan, the private plan is the payer and going outside its rules generally means paying for the care. Under a cost plan, services obtained outside the plan are covered under Original Medicare instead, with the usual Original Medicare cost sharing. That single difference is why the category persisted for so long in particular parts of the country, and it is the thing to understand before comparing a cost plan with anything else.
Where the authority comes from
Cost plans are authorised by section 1876 of the Social Security Act rather than by the Medicare Advantage provisions, which is why the phrase section 1876 cost plan appears in the rules and in the literature. Legislation over the past decade has restricted where they may continue to operate, generally by reference to how much competition from Medicare Advantage exists in the service area, so the category has been shrinking and is now confined to a handful of places.
Reading it against the state picture
Because the restriction is written in terms of local Medicare Advantage competition, the places where cost plans survive tend to be places where Advantage take-up was lower. This site publishes that take-up for every state from CMS's own enrollment file, so a reader can see the underlying pattern the rule keys off, even though the index itself counts Medicare Advantage as a whole rather than naming this category separately.
Questions people ask about what is a medicare cost plan
Is a cost plan the same as Medicare Advantage?
No. It is a different statutory authority, and its defining feature is that care obtained outside the plan falls back to Original Medicare.
Why is it called a section 1876 cost plan?
Because section 1876 of the Social Security Act is the provision that authorises it, separately from the Medicare Advantage provisions.
Are they still available?
In very few places. Legislation restricted where they may operate by reference to local Medicare Advantage competition.
Does this site list them?
No. It names no plan of any kind, and the enrollment file it publishes counts Medicare Advantage as a whole.