Every fall, headlines about Medicare’s Annual Enrollment Period (AEP) flood the news, running October 15 through December 7. But if you’re shopping for a Medigap policy, that calendar doesn’t apply to you the same way — Medigap runs on its own, personal timeline. Confusing the two is one of the most common and costly mistakes new Medicare beneficiaries make. Here’s exactly how Medigap enrollment timing actually works.
What Is the Medigap Open Enrollment Period?
The Medigap Open Enrollment Period is a one-time, 6-month window that begins the first month you are both age 65 or older and enrolled in Medicare Part B. During these six months, federal law guarantees you the right to buy any Medigap policy sold in your state, at that insurer’s best available rate, regardless of your health conditions. Insurers cannot deny you coverage, charge you more because of a pre-existing condition, or make you wait for coverage to begin (except for a limited pre-existing condition waiting period in some cases, discussed below).
Medigap Open Enrollment vs. Medicare’s Annual Enrollment Period
| Feature | Medigap Open Enrollment | Medicare Annual Enrollment (AEP) |
|---|---|---|
| Applies to | Medigap / Medicare Supplement plans | Medicare Advantage & Part D plans |
| Timing | One-time, tied to your 65th birthday + Part B start | Every year, Oct 15 – Dec 7 |
| Length | 6 months | ~7.5 weeks |
| Medical underwriting | Not allowed during this window | Never applies (guaranteed issue year-round) |
| Recurs annually? | No — once per lifetime, generally | Yes, every year |
This is why so many people are surprised to learn there’s no “Medigap AEP” — the October-through-December Medicare marketing blitz you see every fall is almost entirely about Medicare Advantage and Part D, not Medigap. If you’re weighing both paths, our comparison of Medigap vs. Medicare Advantage costs explains how the two enrollment systems connect to your overall decision.
When Exactly Does Your Window Start?
Your personal Medigap Open Enrollment Period begins on the first day of the month in which you are both 65 (or older) and enrolled in Medicare Part B — not Part A alone. For most people this means:
- If you enroll in Part B the month you turn 65, your window starts that same month.
- If you delay Part B (for example, because you had employer coverage), your window doesn’t start until you actually enroll in Part B, even if that’s years after turning 65.
- The window lasts exactly 6 months and does not pause, extend, or reset.
What Happens If You Miss the Window?
Missing your Medigap Open Enrollment Period doesn’t mean you can never get Medigap — it means the guaranteed-issue protections go away in most states. After the window closes, insurers can generally require you to answer health questions (medical underwriting) before selling you a policy. Depending on your health history, an insurer might:
- Charge you a higher premium than someone who enrolled during their window
- Add a waiting period before covering a pre-existing condition
- Deny your application outright
There are important exceptions. Certain life events — like losing employer coverage or a Medicare Advantage plan leaving your area — trigger a Guaranteed Issue Right that reopens guaranteed access to Medigap even outside your original window. We cover every qualifying scenario in Guaranteed Issue Rights for Medigap: When Insurers Can’t Deny You, and explain how underwriting actually works in Medigap Underwriting & Pre-Existing Conditions Explained.
A Handful of States Offer Extra Protections
A small number of states — including Connecticut, Massachusetts, New York, and Maine — have their own rules requiring guaranteed issue Medigap access year-round or with an annual “birthday rule” or “anniversary rule” window to switch plans without underwriting. If you live in one of these states, your options may be broader than the federal minimum described here. Always confirm current state-specific rules with your state insurance department or a licensed agent before assuming you’ve missed your chance.
Should You Enroll the Moment Your Window Opens?
In most cases, yes — enrolling as early as possible in your window locks in guaranteed-issue pricing and coverage before any health changes can complicate your application. That said, it’s worth taking a few weeks to compare plan letters and carrier pricing rather than signing the first policy you see. Review Medigap Plan Letters Explained and check what Medigap costs in your state before committing.
Find out if you’re in your Medigap Open Enrollment window and compare rates now.
Frequently Asked Questions
- Is Medigap Open Enrollment the same as Medicare’s Annual Enrollment Period?
- No. Medicare’s Annual Enrollment Period (October 15 – December 7) applies to Medicare Advantage and Part D. Medigap Open Enrollment is a separate, one-time 6-month window tied to your age and Part B enrollment date.
- What happens if I miss my Medigap Open Enrollment window?
- You can still apply, but in most states insurers may use medical underwriting to charge more or deny coverage, unless a Guaranteed Issue Right applies to your situation.
- Does the Medigap window repeat every year like AEP?
- No. For most people it’s a single, once-in-a-lifetime 6-month window, though some states offer additional annual switching rights.
