Medicare Guide

Medicare Supplement Enrollment Periods

Medicare Supplement enrollment is one of the places where Medicare vocabulary causes real confusion. People hear "open enrollment" and assume there is a yearly Medigap shopping season. For most people, that is not how it works. The key window is usually a one-time 6-month Medigap Open Enrollment Period tied to Part B, and missing it can change the choices available later.

Reviewed by John Schenk, Licensed Insurance Agent since 2008 · Published May 15, 2026 · Last updated August 14, 2026

Quick answer

Your federal Medigap Open Enrollment Period is usually a one-time 6-month window tied to Medicare Part B.

It starts the first month you are both 65 or older and enrolled in Medicare Part B. During that time, you can generally buy any Medigap policy sold in your state without being denied or charged more because of pre-existing health problems. After it ends, underwriting, limited choices, higher prices, or state-specific rules can come into play.

Key takeaways

Medigap Open Enrollment is not the same as Medicare Annual Open Enrollment.
The federal Medigap Open Enrollment Period lasts 6 months and generally does not repeat every year.
The window starts once you are 65 or older and enrolled in Part B, even if you still have employer coverage.
After the window, medical underwriting may apply unless you have a guaranteed issue right or state-specific protection.
Medigap timing should be checked before leaving employer coverage, dropping Medicare Advantage, or trying to change supplement companies.

Medigap timing

The dates that can change your supplement options

This is not the Medicare Advantage or Part D calendar. Medigap timing is about Part B start dates, protected buying rights, state rules, and whether an insurance company can ask health questions.

Federal window

6 monthsStarts the first month you are 65 or older and have Medicare Part B.

Repeats yearly?

NoThis is a one-time period, unlike Medicare Annual Open Enrollment.

GI timing

60 / 63 daysSome federal guaranteed-issue situations use a 60-days-before to 63-days-after application window.

Under 65 rights

State-basedFederal law generally does not require Medigap sales to people under 65; some states add protections.

The Medigap Open Enrollment Period

Under federal law, the Medigap Open Enrollment Period lasts 6 months. It begins the first month you are 65 or older and enrolled in Medicare Part B. Medicare.gov explains that during this time an insurance company cannot refuse to sell you a Medigap policy it offers and cannot use medical underwriting to deny coverage because of pre-existing health problems.

It is not the same as Medicare Annual Open Enrollment

Medicare Annual Open Enrollment runs from October 15 through December 7 and is mostly about Medicare Advantage and Part D changes. It does not give everyone a fresh yearly right to buy any Medigap policy without underwriting. This is one of the most expensive Medicare misunderstandings because people may wait for October, only to learn that October does not solve their Medigap problem.

What happens after the window ends

After the Medigap Open Enrollment Period, you may still be able to apply for a supplement. The difference is that the insurance company may be allowed to review health history, deny the application, offer fewer choices, or charge differently depending on the situation and state law. In plain English: you can often apply later, but applying later may not mean you can buy the policy you want.

Guaranteed issue rights are situation-specific

Certain situations can create Medigap protections, often called guaranteed issue rights or Medigap protections. These can apply when other coverage changes or ends in specific ways, such as some Medicare Advantage plan exits, moves, plan terminations, or lost Medigap coverage that was not your fault. The rules are situation-specific, so keep notices, emails, plan letters, claim denials, and termination documents.

The 60-day and 63-day windows matter

Some federal guaranteed-issue situations require the Medigap application to happen no earlier than 60 days before coverage ends and no later than 63 days after coverage ends. That is a narrow window. If someone waits until after the old coverage is gone and then starts asking questions, they may have already made the supplement path harder.

Employer coverage and Medigap timing

Someone who works past 65 may not need a Medigap policy while active employer coverage is still in place. Medicare.gov says the Medigap Open Enrollment Period starts once Part B starts and lasts 6 months, even if Part B starts while employer coverage is still active. That is why Part B timing and Medigap timing should be reviewed together, not in separate conversations.

Under 65 Medigap rights depend heavily on state rules

People under 65 who have Medicare because of disability or ESRD may have fewer Medigap rights under federal law. Medicare.gov says federal law generally does not require insurance companies to sell Medigap policies to people under 65, though some states do. Anyone under 65 should check state-specific rights before assuming a supplement is available or affordable.

Why this matters before switching paths

Moving from Medicare Advantage back to Original Medicare with a supplement may be possible, but the supplement is not always guaranteed. Some people have trial rights or other protections. Others may face underwriting. Before dropping a plan, people should understand whether they can get the supplement they want, when it would start, and whether Part D needs to be added.

State protections can change the answer

Federal Medigap rights are only the baseline. Some states offer additional protections, birthday rules, anniversary rules, or other ways to change supplements. Other states are stricter. For someone who has moved, has health changes, or wants to switch companies, state law can be the difference between a simple application and a declined one.

A practical way to plan Medigap timing

Start with the Part B effective date. Then mark the 6-month Medigap window. Then check whether employer coverage, Medicare Advantage, Medicaid, disability, ESRD, moving, or a lost policy changes the rules. Finally, compare plan letters and companies before canceling anything. The order matters because the cleanest Medigap answer is often available before the coverage transition, not after.

Coverage paths

The two big Medicare paths people usually compare

The right answer is not the same for everyone. The better question is which path fits the way you use care.

Turning 65 and taking Part B

This is the cleanest Medigap timing for many people. Your one-time federal window starts the first month you are 65 or older and enrolled in Part B, so plan comparisons should happen before the window quietly passes.

How to Enroll in Medicare Medicare Supplement Plans Medicare Supplement Plan Types

Working past 65

Employer coverage can delay the Part B decision, but once Part B starts, the Medigap clock usually starts too. The key is planning Part B and Medigap together.

Still Working at 65?When to Enroll in Medicare Medicare Part B

Leaving Medicare Advantage

Some people have federal Medigap protections when switching back to Original Medicare. Others may face underwriting. Check the Medigap answer before dropping the Advantage plan.

Medicare Advantage vs Medicare Supplement How to Change or Switch Medicare Plans Changing Medicare Supplements

Go deeper

Related Medicare guides

Use this page as your Medicare starting point, then jump into the specific topic that matches your situation.

Common questions

Questions people usually ask next

These answers are a starting point. Medicare details can change based on timing, other coverage, and where you live.

Does Medigap Open Enrollment happen every year?

No. The federal Medigap Open Enrollment Period is a one-time 6-month period that starts when you are 65 or older and enrolled in Part B.

Can I buy a Medicare Supplement after my open enrollment period?

Maybe. Many people can apply later, but medical underwriting may apply unless you have a guaranteed issue right or another state-specific protection.

Is Medicare Annual Open Enrollment a Medigap open enrollment period?

No. Annual Open Enrollment mainly applies to Medicare Advantage and Part D plan changes. It does not automatically give everyone a new Medigap buying right.

What happens if I start Part B while I still have employer coverage?

Your Medigap Open Enrollment Period can still start when Part B starts. That is why people working past 65 should review employer coverage, Part B, and Medigap timing together.

Can I buy a Medigap policy while I have Medicare Advantage?

Generally, Medigap is designed to work with Original Medicare, not Medicare Advantage. If you want to switch paths, review whether you can leave Medicare Advantage and whether you have a Medigap buying right before making the change.

Do under-65 Medicare beneficiaries have the same Medigap rights?

Not always. Federal law generally does not require companies to sell Medigap policies to people under 65, but some states offer additional protections.

Official references

Sources checked for this guide

These guides are written in plain English, but the 2026 cost figures and coverage rules should stay tied to official Medicare and CMS source material.

Medicare.gov: Get ready to buy Medigap Medicare.gov: When can I buy a Medigap policy?Medicare.gov: Medigap basics Medicare.gov: How Medigap works Medicare.gov: Buying a Medigap policy Medicare.gov: Working past 65

About the reviewer

John Schenk · Licensed Insurance Agent since 2008 · Nevada license #603197

John Schenk is a trainer and Agent Relationship Manager for The Medicare Store. He has been a licensed insurance agent since 2008 (Nevada license #603197). He trains and supports agents who sit with Medicare Store clients every day.

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