Medicare Annual Enrollment Period

From October 15 through December 7, anyone with Medicare can change how they get it. There are three moves, and you can make more than one:

• join a Medicare Advantage plan, or leave one and return to Original Medicare;
• switch from one Medicare Advantage plan to another;
• join, switch or drop a Part D prescription drug plan.

One thing this window does not do. It does not open the door to a Medicare Supplement (Medigap) policy regardless of your health. Medigap runs on its own windows and, outside them, on medical underwriting in most states — see how Medigap plans work. Leaving an Advantage plan in the fall on the assumption that a Medigap policy will be waiting in January is a common and expensive misreading, and it is the one mistake on this page that cannot be undone in the new year.

Nothing here requires you to act. The window is an opportunity to look, and the section below is about what you are choosing when you decide not to.

Your plan renews on January 1 — with next year's terms, not this year's. That is the part worth sitting with: the plans change even when you do not.

Every fall, by September 30, your plan must mail you an Annual Notice of Change. It lists what is different in January: the premium, the deductible, the copays, the provider network, and the drug formulary. A plan that fitted you well this year can fit badly next year without you doing anything at all, and the letter describing exactly how arrives before the window opens. Our ANOC explainer walks through it section by section.

Two changes deserve a second look every year, because they are the ones that move real money:

• the drug formulary — a medication can move to a higher tier, gain a prior-authorization requirement, or come off the list entirely;
• the provider network — a doctor or hospital in the network this year may not be in it next year, and Advantage networks are usually where that bites.

Separately, a plan can leave your county altogether. If yours does, you are told in writing in the fall and a Special Enrollment Period comes with it — but the notice is easy to mistake for ordinary mail, and it is not the same letter as the Annual Notice of Change.

Three checks, in this order, answer it for most people.

Start with your prescriptions. Drug coverage is where plans differ most and where the yearly changes land hardest. Take your actual medication list — names, doses, how often — and check it against next year's formulary for the plan you have, then for anything you are considering. A plan with a lower premium and one of your drugs on a higher tier can cost more over a year than the plan you were about to leave.

Then your doctors. If you are in or considering an Advantage plan, confirm each doctor, specialist and hospital you rely on for next year, not this one. Networks are set annually.

Then the total, not the premium. Add the premium, the deductible, the copays you actually expect and, for Advantage, the out-of-pocket maximum that caps a bad year. Our cost estimator puts the government-set parts and the plan parts side by side.

If those three checks come out the same as last year, doing nothing is a reasonable answer. The point of looking is to know that, rather than to assume it.

December 7 is the last day a change can be made for coverage that starts January 1. A few things about it are worth knowing before the first week of December:

The last change on file wins. If you enroll in one plan in October and a different one in November, the November choice is the one that takes effect. You do not need to cancel the first; enrolling in a new drug plan or Advantage plan automatically ends the old one.

You should get it in writing. The plan you joined sends a confirmation, and then a member ID card before coverage begins. If January arrives and neither has, call the plan — and keep using your current coverage until you have confirmation, because the old plan is what is in force until the new one starts.

Dropping a drug plan is a decision with a price. Going without Part D or other creditable drug coverage for 63 days or more adds a permanent late-enrollment penalty of 1% of the national base beneficiary premium ($38.99 in 2026) for every month you were uncovered, for as long as you later hold drug coverage. The Part D penalty calculator works out what a specific gap costs.

What is still open depends on which kind of coverage you have in January, and the difference is larger than most people expect.

If you are in a Medicare Advantage plan, the Medicare Advantage Open Enrollment Period runs January 1 through March 31. It gives you one change: to a different Advantage plan, or back to Original Medicare with a drug plan. Whatever you choose takes effect the first of the following month.

If you are on Original Medicare with a stand-alone drug plan, that window is not open to you. Without a Special Enrollment Period, your next ordinary opportunity is the following fall — which is why the December date carries more weight for some readers than others.

Special Enrollment Periods can still apply. Moving out of a plan's service area, losing employer coverage, a change in your Medicaid or Extra Help status, a declared disaster where you live, or your plan leaving your county each open a window on their own timetable. A 5-star plan in your county can also be joined once between December 8 and November 30. The enrollment hub covers every window in full.

Treat any of these as a starting point to verify rather than a determination: the rules carry per-case and per-state variation, and the cost of guessing wrong is a coverage gap.