Medicare Enrollment Periods Table
| Period | Window | Who it is for |
|---|---|---|
| IEP | 7 months: 3 before your 65th-birthday month, the month itself, 3 after | First-timers signing up for Parts A and B |
| Open Enrollment | October 15 - December 7, every year | Existing enrollees switching Advantage or Part D plans; changes start January 1 |
| General Enrollment | January 1 - March 31 | Missed IEP; coverage starts the month after you sign up, late penalties may apply |
| SEP (employer) | 8 months after job coverage ends | 65+ still working with employer health coverage |
Medicare signups run on four distinct clocks, and mixing them up is expensive: the Initial Enrollment Period is the 7 months around your 65th-birthday month (3 before, the month itself, 3 after); Open Enrollment runs every October 15 through December 7 for plan changes that take effect January 1; General Enrollment is January 1 through March 31 for anyone who missed the first window; and employer-covered workers get an 8-month Special Enrollment Period after job coverage ends. Enter your birth date above and the checker prints your exact IEP window and whether it is open, closed, or still coming.
The stakes are real: sign up late without employer coverage and the Part B late-enrollment penalty adds 10% per full late year to the premium for the rest of your life - which is why the window math deserves a tool rather than a reminder on a fridge calendar.
How to use
- Enter your birth date to compute your personal IEP - the 7-month window centered on your 65th-birthday month.
- If the window is still ahead, the note shows how many days until it opens; signing up early means coverage starts the first of your birthday month.
- Already enrolled? Use the Open Enrollment row - October 15 to December 7 yearly - to switch Advantage or drug plans for a January 1 start.
Frequently asked questions
What happens if I miss my Initial Enrollment Period?
You fall to General Enrollment (January 1 - March 31 each year), your coverage starts the month after you sign up, and unless you qualify for an exception you pick up the Part B late-enrollment penalty: a permanent 10% premium increase for each full 12-month period you were late. Twenty years of perfect coverage later, that penalty is still on the bill - timing is the only cure.
I was born on the first of the month - does my window shift?
Yes, by Social Security's month-of-age rule: if you were born on the first day of any month, you are considered to reach age 65 on the last day of the previous month. Your whole 7-month window therefore shifts one month earlier than the checker's plain arithmetic suggests - treat your IEP as opening one month before your birth-month math and confirm with SSA when you file.
Is Open Enrollment the same as my Initial Enrollment Period?
No - they solve different problems. IEP happens once, around your 65th birthday, and it is how you first get into Medicare. Open Enrollment (October 15 - December 7) happens every year and is only for people already in Medicare who want to switch Medicare Advantage or Part D drug plans, or drop one; changes always land on January 1. Missing Open Enrollment costs you nothing but options - missing IEP costs a lifetime penalty.
I am still working at 65 with employer coverage - when must I sign up?
With active employer health coverage at a company of 20 or more employees, you can delay Parts A and B without penalty and take an 8-month Special Enrollment Period after the job coverage ends for any reason. The trap is retiring first and enrolling later - the 8-month clock starts when coverage ends, not when you stop working, and waiting past it triggers the same permanent 10% Part B penalty.