When does my Medigap Open Enrollment Period start?

Your Medigap Open Enrollment Period starts on the first day of the month in which you are both age 65 or older and enrolled in Medicare Part B. It lasts exactly six months. If you enroll in Part B at age 65 in July, your OEP runs from July 1 through December 31 of that year.

Can I be denied Medigap coverage if I apply outside my Open Enrollment Period?

In most states, yes. Outside of guaranteed-issue situations, insurers can review your health history, charge higher premiums, or deny your application entirely. A few states have birthday rules or other annual windows that restore some switching rights; check with your state insurance department or a SHIP counselor.

What is a guaranteed-issue right and when does it apply?

A guaranteed-issue right means an insurer must sell you a Medigap policy at standard rates without medical underwriting. It applies during your initial six-month Open Enrollment Period and in specific situations afterward, such as when your Medicare Advantage plan leaves your area, when you return to Original Medicare within 12 months of first joining Medicare Advantage, or when your current Medigap insurer goes bankrupt. These rights are usually time-limited to 63 days from the triggering event.

Does Medicare have an annual Medigap open enrollment like it does for Medicare Advantage?

No. Unlike Medicare Advantage, which has an Annual Enrollment Period each fall that allows plan changes with guaranteed-issue rights, Medigap does not have a federally mandated annual open enrollment for most beneficiaries. Your main guaranteed window is the one-time six-month period when you first become eligible. A handful of states add birthday rules or other annual windows on top of federal law.

When Can You Buy or Switch Medigap Plans?

By Naomi Foster, Contributing Writer, Healthcare
Updated July 9, 2026

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The Medigap Open Enrollment Period is the six-month window that begins the month you are both age 65 or older and enrolled in Medicare Part B. During this window, insurers must sell you any Medigap plan they offer in your state at standard rates, with no medical underwriting and no ability to charge more based on health history. After it closes, most people can be denied coverage or charged higher premiums based on their health in most states.

The Medigap Open Enrollment Period

Federal law gives you a one-time, six-month Medigap Open Enrollment Period (OEP). It starts automatically on the first day of the month in which you are at least 65 years old and enrolled in Medicare Part B. You do not need to apply for the OEP; it begins by operation of law.

During the OEP:

Insurers cannot deny you a Medigap policy.
Insurers cannot charge you more because of past or present health problems.
Insurers cannot make you wait for coverage to start (with limited exceptions for pre-existing conditions in some states).
You can choose any standardized Medigap plan available in your state.

Details about the OEP and standardized plan types are at Medicare.gov's Medigap resource page.

What Happens After the Open Enrollment Period?

Once your six-month OEP ends, you lose guaranteed-issue rights in most circumstances. If you want to buy or switch Medigap plans after that point, insurers in most states can:

Review your medical history through a process called medical underwriting.
Decline to sell you a policy based on health conditions.
Charge more than a standard rate because of your health history.
Exclude coverage for pre-existing conditions for a period of time.

This is one of the sharpest practical differences between Medigap and Medicare Advantage: Advantage has an Annual Enrollment Period each fall that lets you switch plans, while Medigap has no equivalent annual window that restores guaranteed-issue rights for most beneficiaries.

Guaranteed-Issue Rights Outside the OEP

Federal law also grants guaranteed-issue rights in specific situations outside the OEP. According to Medicare.gov, these include:

Medicare Advantage plan leaves the area or stops covering Medicare services: you have a right to buy a Medigap policy without underwriting.
You leave a Medicare Advantage plan within 12 months of joining: if you joined for the first time and return to Original Medicare within that window, you can buy Medigap with guaranteed-issue rights.
Your employer-sponsored coverage ends: if you had group health coverage through an employer and it ends, you may qualify for guaranteed-issue rights.
Your Medigap insurer goes bankrupt or otherwise leaves your coverage: you receive a new guaranteed-issue opportunity.
You were misled into joining a Medicare Advantage plan: documented misenrollment may trigger a special right.

These rights are time-limited, typically 63 days from the triggering event. Acting promptly when a qualifying event occurs is necessary to preserve them.

Under-65 Medicare Beneficiaries

People who receive Medicare before age 65 due to disability or conditions such as end-stage renal disease (ESRD) or ALS have different and more limited rights. Federal law does not require all states to offer Medigap to under-65 beneficiaries with guaranteed-issue protections. Some states extend those protections; others do not. When you turn 65 while already on Medicare, you receive a full six-month OEP at that point. Check your state's rules through your State Health Insurance Assistance Program (SHIP) or your state insurance department.

Switching Medigap Plans After Enrollment

If you are already enrolled in a Medigap plan and want to switch to a different plan or carrier, you can apply at any time. Outside of a guaranteed-issue situation, however, the new insurer will almost certainly apply medical underwriting. Do not cancel your current Medigap policy until you have received written acceptance from the new insurer. Canceling first and being denied could leave you without Medigap coverage and without a right to reinstatement.

State Protections That Go Further Than Federal Law

Several states provide Medigap protections beyond federal minimums:

Some states require annual or birthday-rule windows during which beneficiaries can switch Medigap plans without underwriting.
Some states require insurers to offer Medigap to under-65 Medicare beneficiaries.
Some states ban Part B excess charges, which affects the Plan G vs Plan N comparison.

State rules vary considerably, so check with your state's insurance commissioner or a SHIP counselor for your specific situation. CMS maintains enrollment and policy data at CMS.gov.

Planning Around Your Enrollment Window

A few practical steps:

Note your Part B enrollment date. Your six-month OEP clock starts that month.
Compare plans before your OEP begins so you are ready to enroll as soon as the window opens.
Use the Medigap cost calculator to estimate costs for the plans you are considering before you apply.
Contact a free SHIP counselor in your state for personalized guidance. SHIP counselors are not paid commissions.
Verify enrollment details, plan availability, and premium information at Medicare.gov before submitting any application.

Frequently Missed Timing Traps

Two mistakes repeatedly cost beneficiaries their guaranteed-issue rights:

Delaying Part B enrollment: if you delay enrolling in Part B (for example, because you have employer coverage), your OEP does not start until you actually enroll. Delaying without qualifying coverage may result in late enrollment penalties and gaps in coverage; understanding your specific situation matters before you delay.
Testing Medicare Advantage and waiting too long to return: federal law gives you 12 months to return to Original Medicare and keep guaranteed-issue Medigap rights after first joining Medicare Advantage. After that 12-month window, medical underwriting applies in most states.