You can enroll in a Medigap plan during specific windows, and missing them can cost you more or lock you out temporarily

Medicare Supplemental Insurance, also called Medigap, has enrollment periods when you can sign up without waiting or paying a higher premium. The main window is your Initial Enrollment Period, which runs for six months starting the month you turn 65 and enroll in Medicare Part B. Outside that window, you can still enroll, but insurers can charge you more based on your health history, and some plans may not accept you at all.

The rules differ depending on whether you're new to Medicare, switching plans, or losing coverage you already have. Timing matters because the penalties and restrictions are real — a delay of even a few months can mean paying extra for the rest of your life on that plan.

Key Takeaways

  • Your six-month Initial Enrollment Period starts the month you turn 65 and enroll in Medicare Part B, and this is the only time most insurers must accept you without health questions.
  • If you miss your Initial Enrollment Period, you can enroll during the annual Open Enrollment Period (October 15 to December 7 each year), but insurers can charge you more based on how long you went without coverage.
  • Losing employer coverage, moving out of state, or having your current Medigap plan discontinued are "may have access to events" that open a special enrollment window outside the regular periods.
  • The longer you delay after your Initial Enrollment Period ends, the higher your premium penalty will be, and some insurers may deny you coverage entirely.

Your Initial Enrollment Period: The Six-Month Window

Your Initial Enrollment Period is the easiest time to enroll in Medigap. It starts the first day of the month you turn 65 and lasts six months. During this window, insurers cannot turn you down or charge you more because of pre-existing health conditions — this protection is called may provide issue.

To use this period, you must be enrolled in Medicare Part B. If you delay Part B enrollment, your Medigap Initial Enrollment Period is delayed too. For example, if you turn 65 in March but don't enroll in Part B until August, your six-month Medigap window starts in August, not March.

This is the window when you have the most choice and the lowest risk of being denied. If you know you want Medigap coverage, enrolling during this period protects you from future premium increases tied to your health.

Annual Open Enrollment: October 15 to December 7

If you miss your Initial Enrollment Period, you can enroll during the annual Open Enrollment Period, which runs from October 15 to December 7 each year. Coverage begins January 1 of the following year. You can enroll during this window even if you have pre-existing conditions, and insurers must accept you.

However, insurers can charge you a higher premium if you went without Medigap coverage after your Initial Enrollment Period ended. The penalty is typically 10 percent of the plan's base premium for each month you were uninsured. If you waited two years to enroll, you could pay 20 percent more. This surcharge usually stays with you for as long as you keep that plan.

The Open Enrollment Period is your second-best option, but the cost difference can add up quickly. A plan that costs $150 per month could cost $180 per month if you waited two years to enroll.

Special Enrollment Periods: When Life Changes Open New Windows

Certain life events create a special enrollment period outside the regular windows. These include losing employer coverage, moving to a different state, or having your current Medigap plan discontinued by the insurer. If any of these happen, you usually have 60 to 63 days to enroll in a new plan with may provide issue protection.

Losing employer retiree health coverage is one of the most common triggers. If your employer ends your coverage, you have 63 days to enroll in Medigap without health questions and without premium penalties. You will need documentation from your employer showing when coverage ended.

Moving out of state can also open a special enrollment window if your current plan is not available in your new state. Contact your current insurer to confirm whether your move qualifies, and ask them for written confirmation of the date your coverage ends in your old state.

What Happens If You Enroll Late Without a may have access to Event

If you miss your Initial Enrollment Period and do not have a may have access to event, you can still enroll during the next Open Enrollment Period, but you will face a premium penalty. The penalty is calculated as 10 percent of the plan's base premium for each full month you were without Medigap coverage after your Initial Enrollment Period ended.

Some insurers also use medical underwriting, meaning they can review your health history and deny you coverage or offer you only certain plans. This is rare but possible. The longer you wait, the higher the risk that an insurer will limit your options.

The penalty does not go away after a certain number of years — it typically stays for as long as you keep that plan. If you switch to a different Medigap plan later, the new insurer may or may not charge you a penalty, depending on your state's rules.

State Rules and Plan Availability

Medigap rules vary by state. Some states have stricter protections for people who enroll late; others follow the federal minimum. A few states have different enrollment periods or different premium penalty structures.

Not all Medigap plans are available in all states. Plan A, B, C, D, G, K, L, M, and N are standardized across the country, but insurers in your state may not offer all of them. If you move to a new state, your current plan may not be available, which can trigger a special enrollment period.

Contact your state's health insurance counselor or your state insurance commissioner's office to learn the specific rules where you live. These services are free and can answer questions about your state's enrollment rules.

How to Enroll During Your Window

Once you know which enrollment period applies to you, contact Medigap insurers directly. You can call them, visit their websites, or work with an insurance agent. You will need your Medicare card and information about your current coverage (if you have any).

Some people work with a licensed insurance agent who represents multiple insurers. Agents do not charge you a fee — they are paid by the insurance company. Using an agent can save time if you want to compare plans, but you can also contact insurers on your own.

Keep records of when you enroll and which plan you choose. Save your enrollment confirmation and your policy documents. If there is ever a question about when you enrolled or whether you were in your Initial Enrollment Period, these documents protect you.

Frequently Asked Questions

What if I turn 65 but do not enroll in Medicare Part B right away?

Your Medigap Initial Enrollment Period does not start until you enroll in Part B. If you delay Part B, your six-month Medigap window is delayed too. Enroll in Part B as soon as you are may be able to access to start your Medigap window on time.

Can I switch Medigap plans outside the Open Enrollment Period?

Yes, you can switch plans during the annual Open Enrollment Period (October 15 to December 7) without health questions. Outside that window, you can switch only if you have a may have access to event like losing coverage or moving states. Otherwise, the new insurer can deny you or charge more based on your health.

Does the premium penalty ever go away?

No. The 10 percent monthly penalty for late enrollment typically stays for as long as you keep that plan. If you switch to a different Medigap plan, the new insurer may charge a different penalty depending on your state and how long you were uninsured.

What counts as a may have access to event for a special enrollment period?

Losing employer coverage, moving out of state, or having your current Medigap plan discontinued by the insurer are the main may have access to events. You usually have 60 to 63 days to enroll after the event. Contact your current insurer or your state insurance commissioner's office to confirm whether your situation qualifies.

Can an insurer deny me coverage if I enroll during Open Enrollment?

No. During the annual Open Enrollment Period, insurers must accept you regardless of health. However, they can charge you a higher premium if you went without coverage after your Initial Enrollment Period. During other times of year, insurers can deny you or limit which plans you can choose.