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Open Enrollment for Medicare Supplement Plans: Your Window and Your Backup Rights

Reviewed by Russell Noga, Licensed Medicare Insurance Broker (all 50 states) — Last updated November 9, 2026

Open enrollment for Medicare supplement plans is a one-time, six-month period that starts the month you are 65 or older and enrolled in Part B, during which insurers must sell you any Medigap policy they offer at their standard price, with no health questions. It is not the fall Medicare enrollment period from October 15 to December 7, which does not give anyone a right to buy a supplement.

2027 by the Numbers

6 months

length of the Medigap open enrollment period, starting with Part B at 65 or older (Medicare.gov)

63 days

usual deadline to use a federal guaranteed issue right after other coverage ends (Medicare.gov)

16

states with a Medigap birthday rule for current policyholders (KFF, October 2026)

The phrase open enrollment causes more Medigap mistakes than almost any other. Every fall, ads announce Medicare open enrollment, and many people assume it is their chance to buy or change a supplement. For Medigap, the protected window is personal: it is tied to your own Part B start date, it happens once, and in most states nothing reopens it on a calendar.

This page separates the two kinds of open enrollment, spells out what the six-month window does and does not guarantee, and lists the federal and state rights that act as a second chance, including what applies if a Medicare Advantage plan is not renewed for 2027. For exact start-date examples, see when is the Medigap open enrollment period.

✔ Licensed in all 50 states
✔ Based on CMS 2027 data
✔ Free plan comparison

Key Highlights

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The fall enrollment period from October 15 to December 7 covers Medicare Advantage and Part D, not Medigap.

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During your six-month window, insurers cannot deny you or charge more because of health, but a pre-existing waiting period of up to six months can apply without prior coverage.

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Federal guaranteed issue rights list Plans A, B, D, G, K and L, plus C and F for people eligible before 2020, but not Plan N.

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Connecticut and New York allow guaranteed issue year-round, and 16 states have a birthday rule.

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Fall Open Enrollment Is Not Your Medigap Window

Medicare’s fall open enrollment

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Runs October 15 to December 7, 2026, for coverage starting January 1, 2027

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Lets you join, drop or switch Medicare Advantage and Part D plans

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Repeats every year for everyone with Medicare

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Gives no right to buy a Medigap policy without health questions

Medigap open enrollment

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Six months starting the first month you are 65 or older and in Part B

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Lets you buy any Medigap policy sold in your state

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Happens once per person and cannot be restarted

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Bars insurers from using your health to deny you or raise your price

Someone who uses the fall period to leave a Medicare Advantage plan for Original Medicare can still apply for a supplement, but outside a protected window the insurer may ask health questions and decline the application. Dropping the Advantage plan before a Medigap approval is in hand is the classic way people end up with Original Medicare alone.

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What the Six Months Protect, and the One Gap

During your Medigap open enrollment, an insurer may not

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Refuse to sell you any policy letter it offers in your state

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Charge you more than a healthy applicant of the same age, sex and tobacco status

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Ask about your medical history to decide whether to accept you

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Delay the policy because of a health condition

The waiting-period gap: If you had no prior health coverage, an insurer can still decline to pay for a pre-existing condition for up to six months. Each month of creditable coverage before the policy starts, such as an employer plan, shortens that wait by one month, as long as the break in coverage was no longer than 63 days. Six months of prior coverage removes the wait entirely.

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Finding Your Own Start and End Dates

1

Locate your Part B effective date It is printed on your red, white and blue Medicare card and in your Social Security or Railroad Retirement Board letters.

2

Check your age on that date If you are already 65, the window opens on the first day of that month. If Part B starts before 65 because of a disability, the federal window waits until the month you turn 65.

3

Count six full months A Part B start of March 1, 2027 gives a window through August 31, 2027.

4

Apply early enough for a clean start North Carolina’s insurance department suggests applying at least 30 days before you want coverage to begin, so the policy is in force when Part B starts.

Delaying Part B because you are still covered by a current employer delays the window too, since it opens only once Part B begins.

Federal Backup Rights That Work Like a Second Window

Outside open enrollment, federal law gives guaranteed issue rights in specific situations. They are shorter, and they usually limit which letters you can buy.

Situation Letters you can buy When to apply
Your Medicare Advantage plan ends, leaves your area, or you move out of its area, and you return to Original Medicare A, B, D, G, K or L (C and F if eligible before 2020) As early as 60 days before coverage ends, up to 63 days after
Employer, retiree or union coverage that pays after Medicare ends A, B, D, G, K or L (C and F if eligible before 2020) Up to 63 days after the coverage ends, the end notice, or a claim denial, whichever is latest
Trial right: you joined Medicare Advantage at 65 and leave within the first year Any Medigap policy sold in your state As early as 60 days before coverage ends, up to 63 days after
Trial right: you dropped Medigap for the first time for an Advantage plan and leave within a year Your old policy if still sold, otherwise A, B, D, G, K or L (C and F if eligible before 2020) As early as 60 days before coverage ends, up to 63 days after
Your Medigap insurer goes bankrupt or your coverage ends through no fault of yours A, B, D, G, K or L (C and F if eligible before 2020) Up to 63 days after coverage ends

Summary of federal rights as published in Medicare’s guaranteed issue materials. States can add more rights but cannot take these away.

Where Plan N fits: Plan N is not on the federal guaranteed issue list for most of these situations, so someone using a backup right usually chooses Plan G or one of the other listed letters. During the original six-month window, Plan N is available like every other letter an insurer sells.

If Your Medicare Advantage Plan Is Not Renewed for 2027

An Advantage plan that leaves a county or ends sends members a notice in the fall. That ending gives a federal right to buy a supplement without health questions, but only if you return to Original Medicare rather than picking another Advantage plan. You may apply as early as 60 days before the plan’s last day, and the Medigap policy cannot begin until the Advantage coverage has ended.

Practical points for a plan ending December 31, 2026

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Keep the non-renewal notice; insurers can ask for proof of the right.

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Apply so the supplement starts January 1, 2027, to avoid a month with Original Medicare alone.

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Add a stand-alone Part D drug plan during the fall period, because Medigap does not include drug coverage.

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The right usually runs out 63 days after the Advantage coverage ends, which for a December 31 ending falls in early March 2027.

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State Rules That Reopen the Door

Rule States How it works
Year-round guaranteed issue Connecticut, New York Insurers must accept applicants 65 and older at any time of year
Annual window Massachusetts Regulation sets February 1 to March 31, and KFF reports insurers accept applications year-round in practice
Birthday rule California, Delaware, Idaho, Illinois, Indiana, Kentucky, Louisiana, Maryland, Nevada, New Mexico, Oklahoma, Oregon, Utah, Virginia, West Virginia, Wyoming Current policyholders get a window of 30 to 63 days around their birthday, depending on the state, usually limited to equal or lesser benefits
Anniversary rule Missouri Policyholders may move to an equivalent policy with another insurer within 30 days before or after the policy anniversary

Source: KFF review of state Medigap rules, October 2026. Exact windows, eligible letters and conditions vary; confirm with your state insurance department before relying on a state right.

These rules help people who already own a supplement. Someone with no Medigap policy at all usually cannot use a birthday or anniversary rule to buy one. State-by-state switching details are in the Medicare supplement birthday rule.

Missteps That Waste the Window

Waiting for fall

The six months may close long before October, and fall open enrollment will not reopen it.

Starting Part B too early

Taking Part B while still on strong employer coverage starts the one-time clock even if a supplement is not needed yet.

Shopping only one insurer

The same letter can carry very different premiums, and the window is the only time every insurer must accept you.

Picking a letter with no exit plan

Moving to richer coverage later can require health questions in most states.

If the window has passed, the questions insurers may ask are covered in Medigap underwriting questions.

Bottom Line

The Bottom Line

Open enrollment for Medicare supplement plans is a single six-month window tied to your Part B start at 65 or older, not the yearly fall period. Outside it, federal guaranteed issue rights and a handful of state rules are the only routes to buying without health questions, so mark the dates early.

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Frequently Asked Questions

➤ Can I buy a Medicare supplement during the October to December enrollment period?

You can apply at any time, but the fall period gives no special right to a supplement. Unless you are in your six-month window, hold a guaranteed issue right or live in a state with extra protections, the insurer can review your health.

➤ Does Medigap open enrollment start at my birthday or at Part B?

It starts on the first day of the first month you are both 65 or older and enrolled in Part B. For someone already on Part B before 65, it begins the month of the 65th birthday.

➤ Is there a waiting period for pre-existing conditions during open enrollment?

There can be, for up to six months, if you had no creditable coverage before the policy starts. Each month of prior coverage without a break of more than 63 days reduces that wait by a month.

➤ Which letters can I buy if my Medicare Advantage plan is ending?

Federally, Plans A, B, D, G, K and L, plus C and F for people eligible for Medicare before 2020. Some states allow more, and insurers may voluntarily offer others with health questions.

➤ Can I use my Medigap open enrollment twice?

No. It runs once, and enrolling in a Medicare Advantage plan during it does not pause or restart it. A trial right may help if you joined an Advantage plan at 65 and leave within a year.

➤ Do birthday-rule states let anyone buy a supplement?

Generally no. Birthday rules let current Medigap policyholders change policies, often to the same or lesser benefits, during a short window around their birthday.

➤ What proof do I need to use a federal guaranteed issue right?

Keep any letter showing your other coverage ended, such as an Advantage non-renewal notice or an employer termination notice. Insurers may ask for a copy with the application.

➤ Does my spouse share my Medigap open enrollment period?

No. Each person has a separate window based on his or her own age and Part B date, so spouses often have different deadlines.

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☎ 1-855-398-0716

TTY users 711  |  Mon–Fri: 5am–7pm, Sat–Sun: 7am–4pm CT

No obligation to enroll

Find & Compare Plans Online

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This website and MedicarePlansGuide.org are privately owned and operated and are not affiliated with, endorsed by, or connected to the Federal Medicare program or any other government agency. We do not offer every plan available in your area. Currently we represent multiple organizations which offer Medicare Advantage, Medicare Supplement Insurance plans, and Medicare Prescription Drug plans. Not all plans offer all benefits mentioned. Benefits, premiums, deductibles, copayments, coinsurance, exclusions, and limitations may vary by plan, carrier, and location and may change over time.

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