Every Medicare Enrollment Window Explained

The October Annual Enrollment Period gets all the attention — but it's actually just one of several windows that allow you to make changes. Knowing all of them means you're never stuck in a plan that isn't working.

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AEP

Annual Enrollment Period · Oct 15 – Dec 7

The main event

The Annual Enrollment Period (AEP) runs October 15 to December 7 every year. Most Medicare beneficiaries can make any plan change during this window.

What you can do during AEP

Switch from Original Medicare to Medicare Advantage (or back)
Switch from one Medicare Advantage plan to another
Join, switch, or drop a Part D drug plan
Changes take effect January 1 of the following year

What to do before AEP

Review your plan's Annual Notice of Change (arrives by September 30)
Check if your doctors are still in-network for next year
Recheck your medications against your plan's coverage
Compare available plans — new options may be available each year

OEP

Medicare Advantage Open Enrollment · Jan 1 – Mar 31

A second chance after January 1

If your Medicare Advantage plan isn't working out, the Open Enrollment Period (Jan 1 – Mar 31) gives you one chance to switch.

What you can do during OEP

Switch from one Medicare Advantage plan to a different one
Drop Medicare Advantage and return to Original Medicare (and add Part D)
Cannot switch from Original Medicare to Medicare Advantage during OEP
Cannot switch or join a standalone Part D plan unless also switching to Original Medicare
One change only — you get one OEP switch per year

SEPs

Special Enrollment Periods · triggered by life events

You don't have to wait for October

Certain life events trigger a Special Enrollment Period (SEP) — a window to make changes outside the normal enrollment calendar.

Common SEP triggers

Losing employer or union health coverage
Moving to a new address that changes your plan options
Moving into or out of a nursing home or care facility
Qualifying for or losing Medicaid or Extra Help
Your plan leaves Medicare or stops serving your area
Returning from living abroad or being released from incarceration
Each SEP has a limited window — many run two calendar months past the month of the event, but the length depends on which SEP it is
Document your qualifying event — you may need to provide proof

Initial Enrollment Period

The 7-month window when you first become eligible

Your first and most important window

When you first become eligible for Medicare, you have a 7-month Initial Enrollment Period (IEP) centered around your 65th birthday.

The 7-month IEP window

3 months before the month you turn 65
The month you turn 65
3 months after the month you turn 65
Enrolling after your birthday month may delay your coverage start
Missing this window without qualifying coverage elsewhere may trigger permanent late enrollment penalties

Quick reference

Enrollment windows at a glance

AEP (Oct 15 – Dec 7)

Change any Medicare plan. Most common annual window. Changes effective Jan 1.

OEP (Jan 1 – Mar 31)

One switch if you're in Medicare Advantage. Limited options. Changes effective the following month.

SEP (varies)

Triggered by life events. Most run about two months from the event, though timing varies by SEP.

IEP (around your 65th birthday)

7-month window when you first become eligible. Most important to get right — penalties for late enrollment.

Not sure if your situation qualifies for a Special Enrollment Period?

A PharmSurance advisor can check your specific circumstances and help you act within your window before it closes. At no cost to you.

PharmSurance.com

We do not offer every plan available in your area. Any information we provide is limited to those plans we do offer in your area. Please contact Medicare.gov or 1-800-MEDICARE (TTY 1-877-486-2048) to get information on all of your options. If you submit your information on this site, it will be provided to one or more licensed insurance agents, who may call, email, or text you about Medicare Advantage, Medicare Supplement, and Prescription Drug Plan options. This is a general educational overview only, not specific to any plan.