Ask five people when Medicare's "open enrollment" is and you'll likely get five different answers — and all five might be right, because Medicare doesn't have just one enrollment window. It has five, each covering a different situation: turning 65, changing plans for next year, fixing a Medicare Advantage plan you're unhappy with, adding a Medigap policy, or reacting to a life change. Mixing them up is one of the most common (and costly) Medicare mistakes. Here's each one, laid out plainly.
- Oct 15 – Dec 7, 2026: Annual Enrollment Period. Change Medicare Advantage or Part D plans, or move between Original Medicare and Advantage. New coverage starts Jan 1, 2027.
- Dec 7, 2026: Last day to make most changes for 2027.
- Jan 1 – Mar 31, 2027: Medicare Advantage Open Enrollment. One more change if you're already in an Advantage plan.
- Any month: If you have Medicaid or Extra Help, you may qualify for a monthly Special Enrollment Period (details below).
1. Initial Enrollment Period (IEP)
This is your first window into Medicare — a seven-month period centered on your 65th birthday (three months before, your birthday month, and three months after). This is when most people enroll in Part A and Part B for the first time, and choose between Medicare Advantage or Original Medicare plus a Medigap policy.
2. Annual Enrollment Period (AEP)
October 15 – December 7 every year (see our full Annual Enrollment Period guide). This is the big one most people mean when they say "open enrollment." During AEP, you can switch from Original Medicare to a Medicare Advantage plan (or back), change from one Advantage plan to another, or switch Part D drug plans. Changes take effect January 1.
3. Medicare Advantage Open Enrollment Period (MA OEP) — the one people forget
January 1 – March 31 every year. If you're already enrolled in a Medicare Advantage plan, you get one additional chance to switch — either to a different Advantage plan or back to Original Medicare (with the option to add a standalone Part D plan). This window is easy to miss because it isn't advertised nearly as loudly as AEP, but it's a genuine second chance if you picked the wrong plan in the fall.
4. Medigap Open Enrollment Period
A one-time, six-month window that starts the month you're 65 and enrolled in Part B. During this window, you have guaranteed-issue rights — carriers can't turn you down or charge you more because of your health. Unlike the other windows, Medigap has no annual deadline; you can apply any time of year. But outside your initial window, most states allow carriers to use medical underwriting, so timing your first Medigap purchase matters more than people expect.
5. Special Enrollment Periods (SEP)
Life doesn't wait for October. SEPs open outside the usual calendar when specific events happen — moving out of your plan's service area, losing employer coverage, qualifying for Extra Help or Medicaid, or your plan losing its contract with Medicare, among others. A SEP can open a short window (often 2-3 months) to make a plan change tied to that specific event.
Can you change Medicare plans anytime?
Usually not. Outside the windows above, you need a Special Enrollment Period. A few are worth knowing because they're more flexible than people expect:
- Dual-eligible or Extra Help (monthly): If you have both Medicare and Medicaid, or get Extra Help with drug costs, you can make a change once per month. Typically that's switching to Original Medicare with a standalone Part D plan, or into an integrated dual-eligible plan (D-SNP) where one is available. See Medicaid & dual-eligible plans.
- 5-star plan SEP (Dec 8 – Nov 30): You can switch into a plan rated 5 stars once during this period.
- Moving: Moving out of your plan's service area, or to a new area with different plan options, opens a window to change.
- Losing other coverage: Leaving employer or union coverage, or losing Medicaid, opens a window to enroll in or change plans.
Not sure if you qualify? Ask us and we'll check in one call.
Every window at a glance
| Window | When | What it lets you do |
|---|---|---|
| Initial Enrollment (IEP) | 7 months around your 65th birthday | First enroll in Medicare, choose Advantage or Original + Medigap |
| Annual Enrollment (AEP) | Oct 15 – Dec 7 | Switch Advantage, Original Medicare, or Part D plans for next year |
| MA Open Enrollment | Jan 1 – Mar 31 | One extra switch if already in an Advantage plan |
| Medigap Open Enrollment | 6 months after 65 + Part B; no annual deadline after | Buy Medigap with guaranteed-issue rights |
| Special Enrollment (SEP) | Triggered by a qualifying life event | Change plans outside the usual calendar |
Not sure which window applies to you?
Tell us your situation and we'll tell you exactly what you can change right now — free, no pressure.
Ask about my enrollment windowA quick way to figure out where you stand
- Turning 65 soon? You're in your Initial Enrollment Period — the biggest decision window you'll get.
- Already have a plan and it's fall? You're in AEP — this is when to review, not just renew.
- It's January through March and you have Medicare Advantage? You still get one more shot to fix a plan that isn't working.
- Thinking about Medigap for the first time? Check how long it's been since you turned 65 and enrolled in Part B — your guaranteed-issue window may already be ticking.
- Just moved, retired, or lost coverage? Ask us whether that opened a Special Enrollment Period — it often does.
How Honorbrook helps
We're an independent agency, so our only job is helping you use the right window at the right time — not steering you toward a plan that benefits one carrier. If you're not sure which of these five windows applies to you today, that's exactly the kind of question we answer for free, in one phone call.
Local to Northern Virginia? See our Fairfax County Medicare page.
This article is general information, not insurance advice. Enrollment rules and specific dates can vary by situation — a licensed agent can confirm what applies to you.
Medicare help in your state
Honorbrook is licensed in the 11 states below. Plan availability, costs and some rules vary by state and county, so call us at (571) 354-0146 for what applies where you live.