Medicare open enrollment 2026: the exact dates
In short
Medicare's annual open enrollment window runs October 15 through December 7, 2026. Changes made in that window take effect January 1, 2027. The dates are fixed by law and do not move from year to year.
October 15 to December 7 is the one Medicare date that never needs a calendar rule applied to it — it’s the same 54-day window every single year, set directly in the Social Security Act rather than tied to a weekday or a holiday.
What actually happens in this window
Three kinds of changes take effect January 1 of the following year if made between October 15 and December 7:
- Switching from Original Medicare to a Medicare Advantage plan, or back
- Switching from one Medicare Advantage plan to another
- Joining, switching, or dropping a Part D prescription drug plan
Nothing changes automatically. A plan someone is already in renews as-is if no action is taken — the window exists for people who want to change something, not as a re-enrollment requirement.
Why the deadline matters more than it looks like it does
Missing December 7 doesn’t just mean waiting a year in most cases. Part D specifically penalizes a late start: going 63 days or more without creditable drug coverage after first becoming eligible adds a permanent premium surcharge, recalculated for as long as the coverage continues. The open enrollment window is the reliable, no-questions-asked way back in before that penalty compounds further.
The window people confuse this with
Medicare Advantage Open Enrollment runs separately, January 1 through March 31, and it’s narrower: it’s for people already enrolled in a Medicare Advantage plan who want to switch plans or move to Original Medicare. It cannot be used to add Part D coverage from Original Medicare, or to join Medicare Advantage for the first time. Those only happen October 15 through December 7.
Common questions
Do these dates ever shift for weekends or holidays?
No. Unlike a payment date, this is an enrollment window set directly in statute — it runs October 15 through December 7 regardless of what day of the week that falls on.
What can be changed during this window?
Switching between Original Medicare and Medicare Advantage, changing Medicare Advantage plans, joining, switching, or dropping a Part D prescription drug plan.
Is this the same as the Medicare Advantage Open Enrollment Period?
No. There's a second, narrower window from January 1 to March 31 for people already in a Medicare Advantage plan to switch plans or move back to Original Medicare — but that window does not allow adding Part D drug coverage from scratch.
What happens if I miss both windows?
Outside of a qualifying life event (moving, losing other coverage), the next chance is the same October 15 window the following year — and a late Part D enrollment can carry a permanent premium penalty.
Source: Centers for Medicare & Medicaid Services (CMS), Medicare & You handbook · retrieved September 12, 2026