Medicare has several different enrollment windows, and it's important to understand when you can make changes to your coverage. Missing the right window can mean late enrollment penalties, gaps in coverage, or being locked into a plan you don't want for an entire year.
Initial Enrollment Period (IEP)
This is your first opportunity to enroll in Medicare. It's a 7-month window that begins 3 months before the month you turn 65, includes the month of your birthday, and extends 3 months after.
- Enroll in Medicare Part A and Part B
- Join a Medicare Advantage plan or Part D drug plan
- Enroll in a Medicare Supplement plan without medical underwriting
Enrolling during the first 3 months of your IEP (before your birthday month) means your coverage starts on the first day of your birthday month. Enrolling later may delay the start of your coverage.
Annual Enrollment Period (AEP)
Also called the "Open Enrollment Period," the AEP runs October 15 – December 7 every year. Coverage changes take effect January 1.
During AEP you can:
- Switch from Original Medicare to a Medicare Advantage plan
- Switch from Medicare Advantage back to Original Medicare
- Switch from one Medicare Advantage plan to another
- Join, drop, or switch Part D drug plans
Medicare Advantage Open Enrollment Period (OEP)
This runs January 1 – March 31 each year. If you're already enrolled in a Medicare Advantage plan, you can switch to a different MA plan or return to Original Medicare once during this period.
You cannot use the OEP to join a Medicare Advantage plan for the first time if you're currently in Original Medicare.
Special Enrollment Periods (SEP)
Special Enrollment Periods allow you to make coverage changes outside of the standard windows if you experience a qualifying life event. Common qualifying events include:
- Moving to a new area not covered by your current plan
- Losing other health coverage (employer plan, Medicaid, etc.)
- Your plan leaves Medicare or stops covering your area
- Qualifying for Extra Help (Low Income Subsidy)
- Moving into or out of a nursing home or long-term care facility
SEPs typically last 2–3 months from the qualifying event. The exact rules depend on the specific event.
Late Enrollment Penalties
If you don't enroll in Medicare Part B when you're first eligible (and you don't have qualifying employer coverage), you may face a permanent premium penalty of 10% for each 12-month period you delayed. Part D also has a late enrollment penalty.