Six enrollment periods, and they do different things
Most of the confusion around Medicare timing comes from treating "open enrollment" as one event. There are several windows, they open at different times, and each one permits a different change. Being inside the wrong one is the usual reason a change gets refused.
| Window | When | What it lets you do |
|---|---|---|
| Initial Enrollment Period (IEP) | 7 months around your 65th birthday month | Sign up for Part A and Part B for the first time |
| General Enrollment Period | 1 January to 31 March | Sign up for Part B if you missed your IEP and have no SEP |
| Open Enrollment / AEP | 15 October to 7 December | Join, switch or drop a Medicare Advantage or Part D plan for 1 January |
| Medicare Advantage Open Enrollment | 1 January to 31 March | If already in a Medicare Advantage plan, switch once or return to Original Medicare |
| Special Enrollment Period (SEP) | Triggered by an event | Change outside the normal windows after a qualifying event, such as losing employer coverage |
| Medigap Open Enrollment | 6 months from the first month you have Part B and are 65 or over | Buy any Medigap policy sold in your state with no health questions |
Source: Medicare & You 2027, CMS
Medigap open enrollment happens once
The Medigap window is the one worth circling. For six months, starting the first month you are 65 or older and enrolled in Part B, an insurer must sell you any Medigap policy it offers at the same price as someone in good health. No health questions, no refusal.
After that window closes, Florida insurers can use medical underwriting on a Medigap application and can decline you. It does not reopen each year. That is why people who join a Medicare Advantage plan at 65 sometimes find they cannot move to Medigap later, even when their plan has changed around them.
What triggers a Special Enrollment Period
A Special Enrollment Period is opened by something happening, not by the calendar. The common triggers are losing employer coverage, moving out of a plan’s service area, your plan leaving Medicare, and becoming eligible for a program such as Extra Help.
Each trigger has its own length. Leaving employer coverage gives you eight months to sign up for Part B, beginning the month after the employment or the coverage ends, whichever comes first. A plan non-renewal gives you until the last day of February to join another Medicare health plan.
Which window applies to you
If you are approaching 65 and not working, your Initial Enrollment Period is the one that matters. If you are working past 65 with employer coverage, you may be able to delay Part B without penalty, and your SEP starts when that coverage ends.
If you are already on Medicare and simply want to change plans for next year, AEP between 15 October and 7 December is your window.
Frequently asked questions
When is Medicare open enrollment?
Medicare Open Enrollment, often called AEP, runs 15 October to 7 December each year, and the plan you choose starts on 1 January. It is the window for joining, switching or dropping Medicare Advantage and Part D plans.
What is the difference between AEP and Medicare Advantage Open Enrollment?
AEP runs 15 October to 7 December and is open to everyone on Medicare. Medicare Advantage Open Enrollment runs 1 January to 31 March and is only for people already in a Medicare Advantage plan, who can make one change or go back to Original Medicare.
How long is my Initial Enrollment Period?
Seven months: the three months before the month you turn 65, your birthday month, and the three months after. Signing up in the earlier months generally means coverage starts sooner.
Can I buy a Medigap policy at any time?
You can apply at any time, but you are only guaranteed acceptance during your six-month Medigap open enrollment period or when you have a guaranteed issue right. Outside those, a Florida insurer can ask health questions and decline the application.
Sources
This guide explains officially published rules and figures. It is not an insurance quote and not an eligibility determination. Only HealthCare.gov, Medicare.gov, Social Security or the carrier can determine your eligibility and your actual price.
We do not offer every plan available in your area. Any information we provide is limited to those plans we do offer. Please contact Medicare.gov or 1-800-MEDICARE to get information on all of your options. Not connected with or endorsed by the U.S. government or the federal Medicare program.
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