The Fall Window Everyone Knows: AEP
The Annual Enrollment Period runs October 15 through December 7, and it's the everything window: switch between Original Medicare and Medicare Advantage in either direction, change from one Advantage plan to another, join, drop, or switch standalone Part D drug plans. Changes take effect January 1. This is the window your Annual Notice of Change is timed to precede, and it's when the full menu of next year's plans is on the table.
One thing AEP does not do: it doesn't guarantee you a Medigap policy. Medigap runs on its own rules — underwriting applies outside your protected windows year-round, AEP included. That distinction trips people up every fall.
The Winter Window Most People Miss: MA-OEP
From January 1 through March 31, the Medicare Advantage Open Enrollment Period gives people who are already in a Medicare Advantage plan one more move: switch to a different Advantage plan, or drop Advantage entirely and return to Original Medicare (with the ability to add a standalone Part D plan). One change, once per window, effective the first of the month after you switch.
What it doesn't allow matters just as much: you can't use it to move from Original Medicare into Advantage, and you can't switch between standalone Part D plans if you're on Original Medicare. It's exclusively an exit and adjustment window for Advantage members — in effect, a built-in remorse period after January reveals what your plan's changes actually feel like at the pharmacy counter and the doctor's office.
Which Window Fixes Which Mistake
The two windows cover different regrets, and knowing which one applies keeps a bad January from becoming a bad year:
- Your new Advantage plan's network dropped your doctor in January → MA-OEP: switch plans or return to Original Medicare
- Your drug moved to an expensive tier and you're on Original Medicare + Part D → wait for AEP (or check for a Special Enrollment Period)
- You want to try Advantage for the first time → AEP only
- You want out of Advantage and into Medigap → MA-OEP handles the Advantage exit, but the Medigap side may involve underwriting — check whether a trial right applies before you leap
Don't Forget the Third Category: SEPs
Outside both windows, Special Enrollment Periods cover life events — moving, losing employer coverage, plan closures, and more. Between AEP, MA-OEP, and SEPs, more of the calendar is actionable than most people assume; the trick is matching your situation to the right door.
That matching takes an advisor about five minutes. If you're staring at a plan that isn't working, call us before assuming you're stuck until fall — there's a fair chance you aren't.
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