When Should I Enroll in Medicare?
Medicare doesn't have just one enrollment date — it has several, and each one serves a different purpose. Some apply once, around your 65th birthday. Others repeat every year, for people who want to change plans. Missing the wrong one can mean a delay in coverage or a permanent late penalty, so it's worth understanding all five windows below.
The Five Enrollment Windows
Which Window Applies to You?
Initial Enrollment Period (IEP)
7 months, centered on your 65th birthday
A 7-month window: the 3 months before your birthday month, your birthday month itself, and the 3 months after. This is how almost everyone first signs up for Medicare.
See the full timeline →General Enrollment Period (GEP)
January 1 – March 31 each year
A fallback window if you missed your Initial Enrollment Period and don't qualify for a Special Enrollment Period. Coverage starts the month after you enroll, and late penalties may apply.
Learn about late penalties →Special Enrollment Period (SEP)
Typically 8 months after employer coverage ends
Triggered by losing job-based coverage or moving. If you act within the window, there's no late penalty — even if you're well past 65.
Read about working past 65 →Medicare Advantage Open Enrollment (MA OEP)
January 1 – March 31 each year
For people already in a Medicare Advantage plan. You can make one switch — to a different Advantage plan or back to Original Medicare — during this window.
Compare the annual windows →Annual Enrollment Period (Fall Open Enrollment)
October 15 – December 7 each year
The big annual window. Anyone already enrolled can switch Medicare Advantage or Part D drug plans to take effect the following January 1.
See what can change each year →Explore This Section
A detailed look at the 7-month Initial Enrollment Period, with a visual timeline.
What the Fall Open Enrollment Period is, and why it pays to review your plan every year.
Step-by-step instructions for signing up — automatically, manually, or plan by plan.
Whether to keep employer coverage or add Medicare, and the rules that decide it.
How the Part B and Part D late-enrollment penalties work, and how to avoid them.
A simple interactive tool to estimate what a Part B late penalty might look like.