Medicare has several enrollment windows that determine when coverage starts and when you can change it. New enrollees use the Initial, General, or Special Enrollment Periods (IEP, GEP, SEP). Once you're enrolled, the Annual Enrollment Period (AEP) is the main yearly window for changes, with one more chance in early spring for Medicare Advantage members through the Open Enrollment Period (OEP).
Initial Enrollment Period (IEP)
Your Initial Enrollment Period is a 7-month window built around the month you turn 65: the three months before, your birthday month, and the three months after.
The month you sign up determines when your coverage starts:
- Sign up during the three months before you turn 65: Coverage starts the first day of the month you turn 65.
- Sign up during your birthday month or any of the three months after: Coverage starts the first day of the following month.
Most people apply during the three months before their 65th birthday so coverage begins without a gap.
General Enrollment Period (GEP)
If you miss your IEP and don't qualify for a Special Enrollment Period, you can sign up during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage begins the first day of the month after you enroll.
A late enrollment penalty may apply for each 12-month period you were eligible for Part B but didn't sign up. The penalty is added to your Part B premium for as long as you have Medicare.
Special Enrollment Period: leaving employer coverage
If you (or your spouse) were covered by an active employer or union group health plan when you first became eligible for Medicare, you can delay Part B without a late penalty. When that coverage ends, you have an 8-month Special Enrollment Period to sign up for Part B.
The 8 months start the month after employment ends or the month after the group health coverage ends, whichever comes first.
Important: COBRA and retiree health plans do not count as active employer coverage for this purpose. They will not extend your SEP, even if you're still enrolled in them.
The two forms you'll need (CMS-40B and CMS-L564) are explained on Medicare enrollment after age 65: required forms.
Annual Enrollment Period (AEP)
The Annual Enrollment Period, October 15 through December 7, is the main window each year for anyone with Medicare to make plan changes. Coverage changes take effect the following 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, switch, or drop a stand-alone Part D prescription drug plan
You can make multiple changes during AEP; only your final selection by December 7 takes effect.
Medicare Advantage Open Enrollment Period (OEP)
If you're already enrolled in a Medicare Advantage plan, you have one chance each year to change it during the Open Enrollment Period, January 1 through March 31.
During OEP, you can:
- Switch to a different Medicare Advantage plan
- Drop your Medicare Advantage plan and return to Original Medicare (you can also add a stand-alone Part D plan in this window)
You can only make one change during OEP. Coverage from the new plan begins the first day of the following month.
OEP is only available if you already have Medicare Advantage. If you're on Original Medicare and want to switch to a Medicare Advantage plan, you'll need to wait for the next Annual Enrollment Period.
Not sure which enrollment window applies to you? Get in touch and I'll walk through your timing with you.