Miss the Medicare window and you pay for it forever
Most deadlines cost you a late fee. This one adds a percentage to a bill you will pay every month until you die.
Medicare enrollment runs on dates, not on when you get round to it. Miss the first window without a valid reason and the penalty follows you.
Your first window
The Initial Enrollment Period runs seven months. It opens three months before the month you turn 65 and closes three months after it.
Turn 65 in October and it runs 1 July to 31 January. That is the whole window. Nobody chases you.
The other windows
| Window | Dates | What it is for |
|---|---|---|
| Initial Enrollment | 7 months around your 65th | Signing up on time |
| General Enrollment | 1 January to 31 March | The catch-up window if you missed |
| Annual Enrollment | 15 October to 7 December | Changing plans, not first signup |
| Medicare Advantage Open | 1 January to 31 March | Switching or dropping Advantage |
| Special Enrollment | Triggered by an event | Losing job cover, moving, other cases |
What the penalty costs
Part B adds 10% to your premium for each full 12-month period you could have enrolled and did not. The standard Part B premium is $202.90 a month in 2026.
Wait two years and you pay 20% more. Every month. For as long as you hold Part B, which for most people means the rest of their life.
Working past 65 with employer cover is a valid reason, and it opens a Special Enrollment Period. Retiring early and deciding to skip Part B is not. The second group finds out years later.
The three that get missed
- A Special Enrollment Period is not automatic. It has its own deadline after the triggering event. Miss that and you are back to the general window.
- The general window has a lag. You sign up between January and March. Cover starts later, and the penalty is already running.
- Living abroad does not pause it. Medicare covers almost nothing outside the United States, and the clock keeps running anyway.
What to do
Find the month you turn 65 and count back three. That is your date. Put it somewhere you will see it.
If you have employer cover past 65, confirm in writing that it counts as creditable. Then confirm the Special Enrollment Period deadline the day that cover ends.
Sources
Figures are the published prices and public averages named above, correct at the date on this page. Nothing here is legal, tax, medical or financial advice. Prices change and companies fail.