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The Medigap Open Enrollment Period (OEP) is the single most important window for enrolling in a Medicare Supplement (Medigap) plan. It lasts six months and begins automatically on the first day of the month in which you are both age 65 or older and enrolled in Medicare Part B. During this window, you have guaranteed issue rights: no insurer can deny your application, charge you more, or make you wait for coverage due to pre-existing conditions.
This Window Happens Once
The Medigap Open Enrollment Period is a one-time opportunity. Once it ends, you generally must go through medical underwriting to buy a Medigap plan. Insurers can charge higher premiums or deny your application based on your health history. There is no annual Medigap open enrollment period.
When Does Your Medigap OEP Begin?
Your Medigap OEP begins on the first day of the month you are both 65 and enrolled in Part B. If you turn 65 in June and your Part B starts June 1, your OEP runs June 1 through November 30. If you delay Part B enrollment because you have employer coverage, your OEP does not begin until your Part B starts, even if you are already past 65.
| Scenario | Part B Start Date | OEP Window |
|---|---|---|
Turn 65 in June, enroll in Part B at 65 | June 1 | June 1 through November 30 |
Turn 65 in June, delay Part B until retirement at 68 | October 1 (age 68) | October 1 through March 31 (age 69) |
Enroll in Medicare due to disability before 65 | Varies | A new 6-month OEP begins when you turn 65 and enroll in Part B |
Which Plans Can You Buy During Your OEP?
During your OEP, you can buy any standardized Medigap plan sold in your state. The most popular options for new enrollees are Plan G (the most comprehensive plan available to those new to Medicare after January 1, 2020) and Plan N (lower premium with some cost-sharing). Plans C and F, which covered the Part B deductible, are no longer available to new Medicare enrollees.
What Happens After Your OEP Ends?
Once your 6-month OEP closes, buying a Medigap plan requires going through medical underwriting in most states. Insurers can ask about your health history, charge higher premiums based on health conditions, or deny your application entirely. Some states offer additional protections, such as birthday rules that allow annual plan switches without underwriting. Outside of your OEP, you may also qualify for guaranteed issue rights in specific situations, such as losing employer coverage or your Medicare Advantage plan leaving your area.
How to Enroll During Your OEP
To enroll in a Medigap plan during your OEP, compare plans from multiple insurers. Premiums for the same standardized plan vary significantly between companies. An independent insurance broker can help you compare options without charging you extra. Once you choose a plan, complete the application and confirm your Part B effective date. Coverage typically begins the first of the following month.
Can I be denied a Medigap plan during my open enrollment period?
No. During your Medigap OEP, insurers must sell you any plan they offer in your state at standard rates. They cannot ask about your health or deny your application.
Does the Medigap OEP apply to Medicare Advantage plans?
No. The Medigap OEP applies only to Medicare Supplement plans. Medicare Advantage enrollment follows different rules, primarily the Initial Coverage Election Period and the Annual Enrollment Period.
What if I enrolled in Medicare Advantage first and now want to switch to Medigap?
If you enrolled in Medicare Advantage at 65 and want to switch back to Original Medicare with a Medigap plan within your first 12 months, you have a trial right that gives you guaranteed issue access to certain Medigap plans. After 12 months, you will generally need to go through underwriting.
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