Medicare Special Enrollment Periods: Every Qualifying Event Explained

A Medicare special enrollment period (SEP) is a limited window, opened by a specific life event, that lets you sign up for Medicare or change your plan outside the usual dates. Most last 2 to 8 months. Miss one and you may wait until the next general window and pay a lifetime penalty.

There are two separate families of these windows, and mixing them up is the most common way people lose coverage. One family is for Part A and Part B, and Social Security runs it. The other is for Medicare Advantage and Part D drug plans, and the plans and Medicare run it.

This guide lists every qualifying event in both families, with the exact length of each window, the form that proves it, and what happens when a window closes. Every rule was checked on October 27, 2026 against Medicare.gov, Social Security and the current federal regulations in 42 CFR.

Key Takeaways

• Leaving a job or job-based health plan after 65 gives you 8 months to add Part B, but only 2 full months after coverage ends to join a Medicare Advantage or Part D plan.
• COBRA, retiree coverage, VA care and Marketplace plans do not count as current employment coverage, so they never start or stretch the 8-month clock.
• Since 2023, Part B also opens for lost Medicaid, declared disasters, employer or broker misinformation and release from incarceration. Most last 6 months; the incarceration window runs through the 12th month.
• For Part B, prove a work-based window with CMS-40B plus CMS-L564. Use CMS-10797 for the newer exceptional situations.
• People with Medicaid or Extra Help can switch to a stand-alone drug plan once a month. Moving, plan contract changes and 5-star plans also open plan windows.

Who decides whether you qualify for a Medicare special enrollment period?

It depends on what you want to do. For a late Part A or Part B sign-up, Social Security decides under 42 CFR 406 and 407. To join, switch or drop a Medicare Advantage or Part D plan, the plan or Medicare decides under 42 CFR 422.62 and 423.38. The two sets of windows have different lengths.

That split matters because the same event can open both families at once. Losing Medicaid, for example, gives you 6 months after Medicaid ends to add Part B, but your window to change drug coverage is 3 full months. If you work only from the longer clock, the shorter one closes first.

Part B and Part D also have different entry rules. A Medicare Advantage plan requires both Part A and Part B. A stand-alone Part D plan needs only one of them, according to Medicare.gov’s sign-up page. So a missing Part B can quietly block a plan choice you thought you had.

If you are still deciding when to sign up for the first time, start with our guide on when you can enroll in Medicare. This page picks up where that one stops: the events that reopen the door after your first window.

How long does a Medicare special enrollment period last?

Part B windows run from 6 to 12 months after the trigger, with 8 months for the common case of leaving job-based coverage. Plan windows are shorter, usually 2 full months after the event, and 3 months for Medicaid or Extra Help changes. A few plan windows stay open as long as the situation lasts.

The table below collects the main windows in one place. Lengths are quoted from Medicare.gov and the eCFR text current as of October 27, 2026. Where the window starts before the event, such as a plan leaving Medicare, the start is noted.

Qualifying event	What it opens	Window length
Your or your spouse’s job, or the job-based plan, ends	Part A and Part B	8 months after the job or the coverage ends, whichever comes first
Lost Medicaid (on or after Jan. 1, 2023)	Part A and Part B	From the notice until 6 months after Medicaid ends
Declared disaster or emergency kept you from signing up	Part A and Part B	Until 6 months after the declaration ends
Employer, health plan, agent or broker gave you wrong information	Part A and Part B	6 months from the day you tell Social Security
Released from jail or prison	Part A and Part B	Through the last day of the 12th month after the release month
Ended volunteer service abroad	Part A and Part B	6 months
Have TRICARE	Part A and Part B	12 months from Social Security’s notice
Moved out of your plan’s area, or to new plan options	Advantage and Part D	2 full months after the move (from the month before if you tell the plan early)
Left employer or union coverage, including COBRA	Advantage and Part D	2 full months after the month coverage ends
Lost Medicaid, or told you lose Extra Help next year	Advantage and Part D	3 full months from the loss or the notice, whichever is later
Have Medicaid or Extra Help	Stand-alone Part D plan	Once per calendar month
Medicare ends your plan’s contract	Advantage and Part D	1 month before to 2 full months after the contract ends
Plan does not renew	Advantage, Part D, Cost plans	December 8 to the last day of February
A 5-star plan is available	Advantage, Part D, Cost plans	Once, December 8 to November 30

Notice the pattern in the chart. For every event that appears in both families, the Part B window is longer than the plan window. That gap is where most coverage holes come from, and it is the reason this guide treats the two families separately below.

Which events let you add Part B late without a penalty?

Eight situations qualify: ending job-based coverage from your or your spouse’s current work, lost Medicaid, a declared disaster, employer or broker misinformation, release from incarceration, volunteering abroad, TRICARE, and other exceptional conditions Social Security approves. Each has its own deadline.

Working past 65 with a group health plan

This is the original Medicare special enrollment period and still the most used. If you had group coverage based on your own current job or your spouse’s, you can sign up any time while that coverage lasts. After it ends, you get 8 months.

The regulation, 42 CFR 406.24, sets the end precisely. The window closes on the last day of the eighth consecutive month in which you have no group coverage based on current employment. Count from the first month without it.

Your start date depends on when you apply. Sign up while still covered, or in the first full month after coverage ends, and Part B can start the first day of that month or any of the next three months. Sign up in any of the remaining seven months and Part B starts the following month.

Three conditions trip people up:

• Small employers. Social Security says that if your employer has fewer than 20 employees, Medicare generally pays first. In that case, skipping Part B can leave large bills unpaid.
• Disability. If you are under 65 and covered through a family member other than a spouse, the employer must have a large group plan, generally 100 or more employees.
• Kidney failure. This window does not apply if your Medicare is based on End-Stage Renal Disease. It also cannot be used during your Initial Enrollment Period.

Coverage that does not count

Social Security’s fact sheet on the Part B special enrollment period names four kinds of coverage that are not based on current employment: COBRA, retiree health coverage, VA coverage, and individual plans such as Marketplace coverage.

If you have a Health Savings Account, Social Security says to stop contributions at least 6 months before you apply, because premium-free Part A can start up to 6 months before your application date.

The practical effect is that the 8-month clock starts when the job ends, even if COBRA runs for another 18 months. Medicare.gov is plain about it: getting COBRA does not change when the window ends. Losing COBRA or retiree coverage later does not open a new one.

There is one more trap in the regulation. If you let a work-based window pass without signing up, you generally do not get another one, even after a later job. The exception is when group coverage is restored before that window ends.

Exceptional conditions added in 2023

Since January 1, 2023, 42 CFR 407.23 has added windows for people who missed signing up because of events outside their control. Each applies only to events on or after that date, and coverage generally starts the month after you enroll.

• Lost Medicaid. Starts when you are told Medicaid is ending and runs until 6 months after it ends. You can choose for Part B to start the month after you sign up, or back to the date Medicaid ended if you pay the premiums for those months.
• Disaster or emergency. Covers a federal, state or local declaration. It runs until 6 months after the declared end, any extension, or the date it is revoked. It also counts if your representative, guardian or caregiver was the one affected.
• Misinformation. Applies if your employer, group plan, or a plan’s agent or broker gave you wrong information about Part B. It starts the day you tell Social Security and lasts 6 months.
• Release from incarceration. Starts the day you are released and ends the last day of the 12th month after the release month. You can ask for coverage back up to 6 months, but not before release. A halfway house after prison does not count as confinement.
• Other exceptional conditions. Social Security decides case by case, and the window lasts at least 6 months.

These windows are not a general second chance. The regulation requires the event to be outside your control and to have actually caused the missed sign-up. Forgetting, or deciding Part B was too expensive, does not qualify.

Volunteering abroad and TRICARE

Two smaller windows round out the list. If you volunteered outside the U.S. for a tax-exempt group and had health coverage there, you have 6 months after that service or coverage ends. If you have TRICARE, you get 12 months from when Social Security notifies you.

Veterans and military families who also have CHAMPVA should read our CHAMPVA guide to see how that coverage works alongside Medicare.

What counts as a qualifying event for Medicare Advantage or Part D?

Plan windows open when you move, lose other coverage, gain or lose Medicaid or Extra Help, enter or leave a nursing home, or when your plan changes its contract with Medicare. A 5-star plan, a low-rated plan and a few special needs situations open windows too. Most last 2 full months after the event.

These rules live in 42 CFR 422.62 for Medicare Advantage and 42 CFR 423.38 for drug plans. Both were amended in April 2026. The groups below follow the order of Medicare.gov’s official list of plan windows.

You move

• Out of your plan’s service area, or to an area with new options. The window starts when you move and lasts 2 full months after. Tell your plan before you move and it starts the month before the move.
• Back to the U.S. after living abroad. You have 2 full months after the month you return.
• Into or out of a nursing home or rehab hospital. You can join, switch or drop plans for as long as you live there, plus 2 full months after the month you leave.
• Out of jail, with Part A or Part B kept up. You have 2 full calendar months after release to join a plan.

One detail catches people who move out of an Advantage plan’s area. If you do not pick a new plan in time, Medicare.gov says you are dropped back to Original Medicare. Drug coverage can lapse with it, so pick a drug plan before the window closes.

You lose other coverage

• Employer or union coverage ends, including COBRA. You have 2 full months after the month it ends to join a plan. Under the rule, you can also pick a start date up to 3 months after the month you apply.
• Drug coverage stops being creditable. If you lose coverage at least as good as Part D through no fault of your own, you get 2 full months after the loss or the notice, whichever is later. Losing it for not paying premiums does not count.
• You leave a PACE program or a Medicare Cost Plan with drug coverage. Each gives 2 full months after the month you leave.

Your Medicaid or Extra Help changes

People with both Medicare and Medicaid, or with Extra Help, can switch into a stand-alone drug plan once per calendar month. The change takes effect the first of the next month. That includes dropping an Advantage drug plan to return to Original Medicare with a stand-alone drug plan.

The monthly option is not open to someone the plan has flagged as an at-risk beneficiary under a Part D drug management program. The plan sends a letter if that applies. People with full Medicaid can also join or switch to an integrated D-SNP once a month, where one is offered.

A bigger change, such as gaining, losing or changing Medicaid or Extra Help, opens a 3-month window from the change or the notice, whichever is later. The same 3 months apply if you are told you will not qualify for Extra Help next year. See our Extra Help guide for the income limits.

Your plan changes or leaves Medicare

• Medicare ends the plan’s contract. Starts 1 month before the contract ends and lasts 2 full months after.
• The plan ends its contract, or both sides agree to end it. Starts 2 months before and lasts 1 full month after.
• The plan does not renew for next year. December 8 through the last day of February.
• Medicare sanctions the plan. Open until the sanction ends or you switch.
• A state takes over the plan for financial reasons. Open while the state action lasts or until you join another plan.
• A major provider network change. Once per change, from the month you are notified plus 2 more calendar months, if your doctor or facility is leaving.

Your plan’s Annual Notice of Change is often the first warning that a plan is leaving. Our guide to the Medicare Annual Notice of Change shows where that news appears in the letter.

Star ratings

If a 5-star Advantage plan, drug plan or Cost plan serves your area, you can switch to it once between December 8 and November 30 of the plan year. If your plan has scored below 3 stars for 3 years in a row, you can switch at any time while you are in it.

Be careful with the 5-star move. Medicare.gov warns that moving from an Advantage plan with drug coverage to a 5-star plan without it can leave you with no drug coverage until your next window, plus a possible Part D penalty.

Trial rights, special needs plans and errors

• Trial right. If you joined an Advantage plan when first eligible at 65, you can drop it for Original Medicare within 12 months of joining and get special rights to buy a Medigap policy. The same 12 months apply if you dropped a Medigap policy to try your first Advantage plan.
• Chronic condition special needs plans. You can join one that serves your condition at any time. The window closes once you join.
• Losing special needs status. Runs until you join another plan or 3 calendar months after you are disenrolled, whichever is first.
• A federal employee’s error. 2 full months after the month you get the notice from Medicare.
• Disasters. This plan window applies only if the disaster kept you from using another window you were eligible for. It ends 2 full calendar months after the declared end. If no end date is set, the regulation caps it at 14 full months.

Thinking about the trial right? Our Medicare Advantage vs Medigap comparison explains what the Medigap side costs.

Can one event open both kinds of windows at once?

Yes. Retiring, losing Medicaid or a disaster can each open a Part B window and a plan window at the same time, with different end dates. If you sign up for Part A or B through an exceptional condition window, you then get 2 months to join an Advantage or drug plan.

Here is how the retirement case plays out. Say you retire June 30, 2026, and your job-based plan ends the same day. Your Part B clock counts July as month one, so it closes on the last day of February 2027, the eighth month without work coverage.

Your plan clock is far shorter. Two full months after June means the window to join an Advantage or drug plan ends August 31, 2026. A plan chosen in June can start July 1; one chosen in July starts August 1 at the earliest.

If you put off Part B until fall, you still get a new Advantage window around your Part B start date. A stand-alone drug plan has no second chance, though: miss August 31 and you wait for fall Open Enrollment, possibly with a gap in drug coverage.

The safer path is to apply for Part B in June or July, with a July 1 start, then pick a plan right away. Keep drug coverage continuous as well. Going 63 days or more without creditable drug coverage triggers the Part D penalty, which we explain in our Part D costs guide.

For the exceptional conditions, Medicare.gov describes the link directly. Once you sign up for Part A or Part B in one of those windows, you have 2 months to join a plan, and coverage starts the month after the plan receives your request. The plan rules count those 2 months from your Part A or Part B start date.

How do you prove you qualify?

For a work-based Part B window, send form CMS-40B with form CMS-L564, which your employer signs, or apply online at SSA.gov. For lost Medicaid, disasters, misinformation and release from incarceration, use form CMS-10797 with written proof. For plan windows, the plan or 1-800-MEDICARE checks your situation.

CMS-40B and CMS-L564 for job-based coverage

Form CMS-40B is the application for Part B when you already have Part A. Form CMS-L564, revised March 2025, is the proof. You fill in Section A, and your employer fills in Section B with the dates your coverage and employment started and ended.

The form states the eligibility test directly: you must have had group coverage through your or your spouse’s current job since you were first eligible for Part B, and that coverage must not have ended more than 8 months ago.

You have three ways to send them, according to Social Security:

1. Online. Use the Part B only sign-up page and upload your evidence. SSA says you can apply any time of year during this window.
2. Fax both forms to your local Social Security office.
3. Mail both forms to that office. Find it at SSA.gov/locator.

Write “I want Part B coverage to begin (MM/YY)” in the remarks section of CMS-40B or the online form. That line tells Social Security which start month you want, which matters most if you are retiring soon.

If your old employer will not or cannot sign Section B, complete it as best you can and attach secondary evidence. A letter, fax or email from the employer or plan also works in place of the form. Social Security accepts any of these:

• Income tax returns that show health insurance premiums paid
• W-2s showing pre-tax medical contributions
• Pay stubs showing health insurance premium deductions
• Health insurance cards with a policy effective date
• Explanations of benefits paid by the group plan
• Statements or receipts showing premium payments

CMS-10797 for exceptional conditions

The newer windows use the CMS-10797 application, mailed or faxed to your local Social Security office. You check the situation that applies and attach written proof that something outside your control kept you from signing up.

• Lost Medicaid: attach a notice from your state or plan showing the end date. If you have none, the form says Social Security will contact your state to confirm it.
• Misinformation: attach the letter or web notice, which must show you got the wrong information before your earlier window ended. Without documents, use the attestation statement on page 5 of the form.
• Disaster: give the declaration’s start and end dates.
• Release: give your incarceration and release dates.

Proving a plan window

For most plan windows, you apply to the new plan directly or call 1-800-MEDICARE (1-800-633-4227, TTY 1-877-486-2048).

Under 42 CFR 422.62, some windows need Medicare approval first: sanctions, creditable coverage notice failures, contract violations and the case-by-case “exceptional circumstances” window. A federal error window starts once Medicare approves it. Keep the letter that triggered your window, such as a non-renewal notice.

What happens if your Medicare special enrollment period runs out?

For Part B, you wait for the General Enrollment Period, January 1 to March 31, with coverage starting the month after you sign up, and you may owe a lifetime penalty. For plans, you wait for fall Open Enrollment, October 15 to December 7, unless another qualifying event comes first.

The Part B penalty is 10% of the standard premium for each full 12 months you could have had Part B but did not. Medicare.gov’s own example: after 24 months, you pay 20% extra. With the 2026 standard premium of $202.90, that is $243.50 a month, rounded, and it usually lasts as long as you have Part B.

For the full math on all three penalties, and how Extra Help or a Medicare Savings Program can take one away, see our Medicare late enrollment penalty guide.

The Part D penalty is 1% of the national base beneficiary premium for each month without creditable coverage. In 2026 the base is $38.99, so 14 months late adds $5.50 a month. If you must buy Part A, a late start can raise its premium 10% for twice the years you waited.

The 2027 Part B premium has not been announced as of October 27, 2026; CMS usually publishes it in the fall. The 2027 Part D base premium is already set at $41.33, so the same 14-month gap would add about $5.80 a month in 2027.

Our Part B premium guide covers the 2026 income brackets.

Low income changes the math. Medicare.gov says you generally do not pay a Part B penalty if you enroll in a Medicare Savings Program. Check the limits in our Medicare Savings Programs guide.

Which situations do not count as qualifying events?

Medicare.gov lists four that do not open a Part B window: your COBRA or retiree coverage ends, you missed your 8-month window after leaving work, you have or lose Marketplace coverage, or you have End-Stage Renal Disease. Simply forgetting or deciding to wait also does not qualify.

Marketplace coverage deserves a special warning. Having a HealthCare.gov plan at 65 does not hold your Medicare place. Treat your Initial Enrollment Period as your real deadline and end the Marketplace plan when Medicare begins.

On the plan side, voluntarily dropping drug coverage or losing it because premiums went unpaid does not create a window either. The creditable coverage rule only covers losses that are involuntary.

Who can check your dates for free?

Your State Health Insurance Assistance Program offers free, unbiased Medicare counseling; find yours at shiphelp.org. For Part A and Part B questions, call Social Security at 1-800-772-1213 (TTY 1-800-325-0778). For plan windows, call 1-800-MEDICARE.

Bring dates when you call: when your job and job coverage ended, when Medicaid ended, or when you moved. Every window in this guide is counted from a specific month, and the person helping you will need it.

Related reading

• Medicare explained: Parts A, B, C and D
• Medicare Open Enrollment dates and what you can change
• Medicare Part A premium and the buy-in rates
• Medicare vs Medicaid: how the two work together