Medicare Special Enrollment Periods: Qualifying Events and Deadlines

What Is a Medicare Special Enrollment Period?

A Medicare Special Enrollment Period (SEP) is an event-driven window that lets you sign up for or change Medicare coverage outside the normal enrollment periods. Unlike the fixed calendar dates that apply to everyone, SEPs open only when you experience a qualifying life event, such as losing employer coverage, moving, or losing Medicaid.

The main advantage of using an SEP is that it usually lets you enroll without a late enrollment penalty, as long as you act inside the window. If you miss the SEP, you may have to wait for the General Enrollment Period (January 1 through March 31) and could owe a lifetime Part B premium surcharge of 10% of the standard premium for every 12 months you delayed. With the 2026 standard Part B premium at $202.90 (up from $185.00 in 2025), that works out to about $20.29 per month per year of delay, for life. Understanding Medicare late enrollment penalties is essential before you decide to delay any part of Medicare.

How SEPs differ from IEP and AEP

The Initial Enrollment Period (IEP) is your one-time, 7-month window around your 65th birthday. The Annual Enrollment Period (AEP) runs October 15 through December 7 every year and lets current beneficiaries change Medicare Advantage or Part D plans. SEPs are neither. They are additional chances to enroll or switch when life throws you a curveball.

Learn more about what you can change during the Medicare Annual Enrollment Period so you know when an SEP is truly needed.

The 8-Month SEP After Employer Coverage Ends

The most commonly used SEP is the 8-month window that opens when you lose active group health coverage based on current employment. This is the SEP that lets people who delayed Medicare while working past 65 enroll in Part A and Part B without penalty. CMS did not change this rule for 2026, so the 8-month timeline in the Medicare & You 2026 handbook still applies.

The 8-month clock starts the month after either your employment ends or your employer group coverage ends, whichever happens first. If you retire on June 30, 2026 and your group plan ends the same day, your SEP runs July 1, 2026 through February 28, 2027.

What you can enroll in during this SEP

• Part A (if you have to buy it because you don't qualify premium-free)
• Part B with no late enrollment penalty
• Part C (Medicare Advantage) or Part D, but only within the first 2 months of the 8-month window to avoid a Part D drug penalty

Note that COBRA drug coverage can be creditable for Part D purposes if it meets Medicare's standard, which means you may be able to delay Part D without a drug penalty while on COBRA. But Part B is a different story, and the 8-month clock keeps ticking. See our full breakdown of how Medicare coordinates with other insurance if you have COBRA, retiree, VA, or TRICARE coverage.

Part C and Part D SEPs: Common Qualifying Events

For people already enrolled in Medicare Advantage or Part D, most SEPs last 2 months from the qualifying event. Here are the most common triggers for 2026.

Moving out of your plan's service area

If you move to an address that's outside your Medicare Advantage or Part D plan's service area, or to an area with new plan options, you get a 2-month SEP to switch plans or return to Original Medicare. If you tell your plan before you move, the SEP starts the month before the move and lasts 2 full months after. If you notify them after, it starts the month you move.

Losing Medicaid (two different SEPs)

Losing Medicaid actually triggers two overlapping SEPs, and it is important to know the difference:

• Part B (and premium Part A) exceptional-conditions SEP: 6 months. If you lose Medicaid coverage on or after January 1, 2023, the SEP starts the day you're notified that your Medicaid coverage is ending and ends 6 months after your Medicaid coverage terminates. You can also choose either a prospective coverage start date or a retroactive start back to the first day of the month you lost Medicaid.
• Medicare Advantage and Part D SEP: 3 months. Per Medicare.gov's 2026 rules, when you're no longer eligible for Medicaid you get 3 full months to join, switch, or drop an MA or Part D plan, measured from either the date you lose eligibility or the date you're notified, whichever is later.

Dual eligibles and Extra Help (monthly SEP)

Since January 1, 2025, CMS replaced the old quarterly Dual/LIS SEP with a once-per-month SEP for people who have Medicaid (full or partial), a Medicare Savings Program, or Extra Help. This monthly SEP continues in 2026. CMS describes it as allowing full-benefit duals, partial-benefit duals, and other LIS-eligible individuals to enroll once per month into a standalone PDP, but it does not permit enrollment into MA-PD plans or changes between MA-PD plans. Full-benefit dual eligibles also get a separate monthly Integrated Care SEP to enroll in an aligned integrated D-SNP (FIDE, HIDE, or AIP) that coordinates with their Medicaid managed care plan.

Plan termination or non-renewal

If your Medicare Advantage or Part D plan leaves Medicare or drops your service area, you get an SEP running December 8 through the last day of February to pick a new plan. The 2026 plan year saw a record wave of terminations: about 13% of beneficiaries enrolled in individual MA-PDs, or roughly 2.6 million people, are in a plan that has been terminated for 2026, an increase from 2025 when nearly 1.3 million Medicare Advantage enrollees faced a termination. Broader estimates that include service-area reductions push the total closer to 2.9 million affected enrollees. If you were involuntarily disenrolled, you may also have guaranteed-issue rights to switch to Medigap.

Moving into or out of an institution

Residents of skilled nursing facilities, long-term care hospitals, and similar qualified institutions get an ongoing SEP that lets them enroll in, switch, or drop a Medicare Advantage or Part D plan at any time. The SEP continues for 2 full months after you move out.

The 5-star SEP

The 5-star Special Enrollment Period runs December 8 to November 30 the following year, and you can use it once per year to switch to a Medicare Advantage or Part D plan with an overall 5-star quality rating, if one is available in your area. Coverage begins the first day of the month after the plan receives your request.

New for 2026: Plan Finder provider directory SEP

CMS announced on September 12, 2025 a new temporary Special Enrollment Period available for beneficiaries who make choices based on incorrect provider directory information in the Medicare Plan Finder (MPF). The parameters: the beneficiary must have enrolled in an MA plan via Plan Finder based on incorrect network information, the MA plan effective date must fall between January 1 and December 1, 2026, and the beneficiary must discover the directory inaccuracy within 3 months of the effective date. This SEP is used by calling 1-800-MEDICARE and lets you switch plans prospectively. It is temporary and applies only to 2026 plan-year enrollments.

Effective Dates and How to Apply

When your new coverage starts depends on which SEP you use and when you file. Here is a snapshot for 2026.

How to apply for the Part B SEP

To use the 8-month employer SEP, you enroll through the Social Security Administration:

1. Complete Form CMS-40B (Application for Enrollment in Medicare Part B). You can file online at SSA.gov, by mail, by fax, or in person.
2. Complete the first section of Form CMS-L564 (Request for Employment Information).
3. Have your employer (or your spouse's employer) fill out and sign the employer section of CMS-L564. This is the proof Social Security uses to verify you had group coverage based on current employment.
4. Submit both forms to Social Security together.

If your employer refuses or is unavailable, Social Security may accept alternative proof such as pay stubs showing health insurance deductions, W-2s, or a letter from the employer, but the completed CMS-L564 is the standard document CMS expects. For a full walk-through, see our step-by-step guide to enrolling in Medicare for the first time.

How to apply for a Medicare Advantage or Part D SEP

For Part C and Part D SEPs, you contact the plan directly or use Medicare.gov Plan Finder. You'll usually need to attest to the qualifying event (such as a new ZIP code for a move) and may be asked for supporting documentation. Most SEP enrollments process in 5 to 10 business days.

SEPs vs Medigap Rules: An Important Distinction

Medicare SEPs apply to Parts A, B, C, and D. They do not automatically give you the right to buy a Medicare Supplement (Medigap) policy. Medigap has its own separate rules, including the one-time 6-month Medigap Open Enrollment Period that begins when you enroll in Part B at age 65.

However, some SEP-triggering events (like an involuntary Medicare Advantage plan termination or a move out of a plan's service area) can create federal guaranteed-issue rights for Medigap. State birthday rules and trial rights can extend those protections further. If you're using an SEP to leave Medicare Advantage, make sure you understand the Medigap underwriting rules in your state before you drop your MA plan.

Frequently Asked Questions

How long is the Medicare Special Enrollment Period after losing employer coverage?

The Part B SEP lasts 8 months. The clock starts the month after your active employment ends or your employer group coverage ends, whichever happens first. If you want to add a Medicare Advantage or Part D plan without a drug penalty, you need to enroll within the first 2 months of that 8-month window.

Does COBRA count as creditable coverage for Medicare?

For Part B, no. COBRA is continuation coverage, not coverage based on current employment, so it does not extend the 8-month Part B SEP or protect you from the Part B late enrollment penalty. For Part D, COBRA drug coverage can be creditable if it meets Medicare's standard, which allows you to delay Part D without a drug penalty in some cases.

How long is the SEP after losing Medicaid?

There are two different windows. For Medicare Part B and premium Part A, the exceptional-conditions SEP lasts 6 months and starts the day you are notified Medicaid is ending. For changing your Medicare Advantage or Part D plan, Medicare.gov gives you 3 full months from the date you lose Medicaid or the date you are notified, whichever is later.

What is Form CMS-L564 and who fills it out?

CMS-L564 is the Request for Employment Information form. You complete Section A yourself, and your employer (or your spouse's employer) completes Section B to verify that you had group health coverage based on current employment. You submit it to Social Security together with CMS-40B to enroll in Part B under a Special Enrollment Period.

Can I switch Medicare Advantage plans after I move?

Yes. Moving out of your plan's service area, or to an area with different plan options, triggers a 2-month SEP to switch plans or return to Original Medicare. If you notify your plan before the move, the SEP starts the month before the move. If you notify them after, it starts the month you moved, and coverage begins the first of the month after the new plan receives your request.

What happens if I miss my Special Enrollment Period?

If you miss the 8-month Part B SEP, you generally have to wait for the General Enrollment Period (January 1 through March 31), with coverage starting the first of the month after you enroll. You may also owe a Part B late enrollment penalty of 10% of the standard $202.90 premium for each full 12-month period you were eligible but not enrolled, and that surcharge lasts for as long as you have Part B.