08/31/2026
Open Enrollment vs. Annual Enrollment — What's the Difference?
"Open Enrollment" and "Annual Enrollment" get used interchangeably, but they're not the same thing. Here's the difference:
Annual Enrollment Period (AEP): Oct 15 – Dec 7 Available to everyone with Medicare. You can switch between Original Medicare and Medicare Advantage, change Advantage plans, or change Part D drug plans. Changes take effect Jan 1.
Medicare Advantage Open Enrollment Period (MA OEP): Jan 1 – Mar 31 Only for people already enrolled in a Medicare Advantage plan. You can switch to a different Advantage plan or drop Advantage and return to Original Medicare (plus add a Part D plan). You get one change during this window.
The mix-up causes real problems — people think they still have options in February that were actually only available during AEP in the fall, or they miss the MA OEP window because they assume it's the same as AEP.
Knowing which window you're in determines what changes are actually available to you.