Losing a job at 65 or older starts an 8-month clock to enroll in Medicare Part B without a penalty, and a separate, shorter 63-day clock for Part D drug coverage. The two deadlines run on different timelines, and the biggest mistake people make is assuming COBRA buys them more time. It does not. If you are 65 or older, had Medicare available to you, and just lost your job, the coverage decisions you make in the next 60 days can lock in a monthly premium penalty for the rest of your life. Here is exactly how the job loss Special Enrollment Period works, why COBRA and retiree coverage are traps, and the paperwork that protects you.
If you have not already reviewed the full list of Medicare qualifying life events, start with the Medicare Special Enrollment Period 2026 guide for the complete picture. This article goes deep on the one scenario that trips up the most people: losing employer coverage through job loss, layoff, or retirement.
The Two Clocks: Part B (8 Months) and Part D (63 Days)
When you lose group health coverage tied to current employment, two separate enrollment windows open at the same time, and they are not the same length.
Part B Special Enrollment Period: 8 months. This window starts the month after your employment ends or your group health coverage ends, whichever happens first. You get 8 months to enroll in Part B without triggering the late enrollment penalty. This is the window most people know about because it is the longer one.
Part D (and Medicare Advantage) Special Enrollment Period: 63 days. This window is much tighter. You have about 63 days after your employer drug coverage ends to enroll in a standalone Part D plan or a Medicare Advantage plan with drug coverage, without a gap that starts the Part D late penalty clock.
The trap here is obvious once you see it: someone who waits 6 months into their 8-month Part B window to enroll may have already blown past their 63-day Part D window by 4 months. You cannot treat these as one deadline. Mark both dates the day your coverage ends.
| Coverage type | SEP length | Starts when |
|---|
| Medicare Part B | 8 months | Month after employment OR group coverage ends, whichever is first |
| Medicare Part D / Medicare Advantage | 63 days | Employer creditable drug coverage ends |
Why COBRA Does Not Extend Your Medicare Deadline
This is the single most expensive misunderstanding in Medicare enrollment. COBRA lets you keep your former employer's group health plan for up to 18 months after you leave a job, and it feels like continuous coverage. For Medicare's purposes, it is not.
Medicare only recognizes coverage based on current employment, meaning you or your spouse are actively working and the coverage comes from that active job. The moment you leave the job, whether by layoff, resignation, or retirement, that coverage stops being "current employment" coverage even if you elect COBRA to keep the same plan. COBRA is a continuation of a plan you are no longer actively working for. Medicare treats it the same as if you had no coverage at all.
That means your 8-month Part B SEP clock starts the month your employment ends (or the group coverage ends), not the month your COBRA runs out. If you elect 18 months of COBRA and wait for it to expire before signing up for Medicare, you will have missed your Special Enrollment Period by roughly 10 months. At that point you can only enroll during the General Enrollment Period (January 1 to March 31, with coverage starting the following month), and you will owe a Part B late enrollment penalty of 10 percent for every full 12-month period you went without Part B or other creditable coverage. That penalty is added to your premium and never goes away, for as long as you have Medicare.
Some COBRA and retiree plans will also refuse to keep paying claims as your primary insurance once you are Medicare-eligible and did not enroll on time, so you can end up with a coverage gap on top of the penalty.
Bottom line: if you lose your job at 65 or older, your SEP clock starts immediately, regardless of whether you elect COBRA. Do not wait for COBRA to run out to sign up for Medicare.
Retiree Health Coverage Works the Same Way
The same trap applies to retiree health benefits from a former employer. Retiree coverage is not coverage based on current employment, so it does not extend your SEP and it is not creditable coverage that lets you delay Medicare without penalty. If you retire and your employer offers you a retiree health plan, your 8-month Part B SEP still starts the month you retire (or the month your active group coverage ends), regardless of the retiree plan.
Many retiree plans are actually designed to work alongside Medicare, paying secondary to Medicare rather than as your primary insurance. If you keep only retiree coverage and skip Part B, you may find claims going unpaid because the retiree plan assumes Medicare is covering the primary share.
Who Actually Qualifies for This SEP
The job loss SEP only applies if your coverage was through active current employment, and specific rules apply to the size of the employer:
- Employer with 20 or more employees: the group health plan is primary to Medicare while you are working. This is the standard case where the 8-month SEP applies cleanly.
- Employer with fewer than 20 employees: Medicare is usually primary even while you are still working, which generally means you should have already enrolled in Part B at 65 rather than delaying. Talk to your HR department and Social Security before assuming this SEP applies to you.
- Spouse's coverage: if you delayed Medicare because you were covered under a spouse's active employer plan, and your spouse loses that job or retires, you get the same 8-month SEP.
- COBRA-only or retiree-only coverage: does not qualify you for this SEP, as explained above.
The CMS-L564 Form: Your Proof of Coverage
To use the Part B Special Enrollment Period, Social Security needs proof that you had qualifying group health coverage based on current employment. That proof is Form CMS-L564, "Request for Employment Information."
Here is how it works:
- You complete Section A of the CMS-L564 with your basic information.
- Your employer completes Section B, confirming your dates of employment and group health coverage.
- You submit the completed form along with Form CMS-40B (Application for Enrollment in Medicare Part B) to your local Social Security office, either by mail, fax, or in person.
- If your employer is unable or unwilling to complete Section B (common with employers that have closed or with very small HR departments), you can submit alternate proof such as pay stubs showing health insurance deductions, W-2s reflecting health benefits, or plan documents, along with a written statement.
Submit these forms as early in your 8-month window as possible. Processing can take several weeks, and you want your Part B coverage to start without a gap.
Step-by-Step: What to Do the Week You Lose Your Job
- Confirm your last day of active employment and the exact date your group health coverage ends. These may not be the same day. Your coverage might run through the end of the month even if your last workday was earlier.
- Mark both deadlines on a calendar: 8 months from that date for Part B, and roughly 63 days from that date for Part D or Medicare Advantage.
- Decide whether to elect COBRA as a short-term bridge only, not as a substitute for enrolling in Medicare. COBRA can make sense to cover a spouse or dependent, or to bridge a few weeks while your Medicare paperwork processes, but it should not delay your Medicare enrollment.
- Get your CMS-L564 form signed by your former employer before your HR contact changes or the company loses track of your records.
- Apply for Part B using Form CMS-40B plus your completed CMS-L564, through Social Security's online portal, by mail, or at a local Social Security office.
- Shop for a Part D plan or Medicare Advantage plan within your 63-day window. Compare plans through Medicare's Plan Finder tool based on your current medications.
- Consider a Medigap policy. Losing employer coverage also opens a one-time Medigap guaranteed issue right in most cases, letting you buy a supplement plan without medical underwriting if you apply within 63 days of your employer coverage ending.
What Happens If You Miss the Window
Missing your 8-month Part B SEP means you are locked out of Medicare until the next General Enrollment Period, which runs January 1 through March 31 each year, with coverage starting the month after you enroll. On top of the wait, you face a permanent Part B late enrollment penalty of 10 percent for each full 12-month period you went without Part B or other creditable coverage after you were first eligible.
Missing your 63-day Part D window works similarly. If you go 63 days or more without Part D or other creditable drug coverage, the Part D late enrollment penalty kicks in: 1 percent of the national base beneficiary premium, $38.99 in 2026, multiplied by the number of full months you went without coverage. That amount is added to your monthly Part D premium permanently, for as long as you have Part D coverage.
Both penalties compound the longer you wait, and neither one is negotiable or waivable except in narrow hardship circumstances that Social Security reviews case by case.
Frequently Asked Questions
Does COBRA count as creditable coverage for Medicare Part B?
No. COBRA is a continuation of a former employer's group plan, not coverage based on current employment, so it does not extend your 8-month Part B Special Enrollment Period and it does not protect you from the late enrollment penalty if you rely on it past your SEP.
How long do I have to enroll in Medicare after losing my job?
You have an 8-month Special Enrollment Period for Part B, starting the month after your employment or group coverage ends, whichever comes first. For Part D or Medicare Advantage drug coverage, you have approximately 63 days from when your employer drug coverage ends.
What is the CMS-L564 form and do I need it?
Form CMS-L564 is proof of your prior group health coverage based on current employment. Your former employer completes part of it, and you submit it with your Part B application to Social Security to document that you qualify for the job loss Special Enrollment Period.
Can I use retiree health coverage instead of enrolling in Medicare?
Retiree coverage is not considered coverage based on current employment and does not extend your Medicare enrollment window. If you retire, your 8-month Part B SEP starts immediately, regardless of any retiree health plan your former employer offers.
What if my employer won't fill out the CMS-L564 form?
You can submit alternate documentation to Social Security instead, such as W-2 forms showing health plan contributions, pay stubs with insurance deductions, or benefit plan summaries, along with a written explanation of why the employer form is unavailable.
Will I owe a penalty if I sign up for Part B within my 8-month window?
No. Enrolling in Part B any time during your 8-month Special Enrollment Period, even in the final month, avoids the late enrollment penalty entirely, as long as you can document that you had qualifying employer coverage the whole time you delayed.
Does losing my job also let me buy a Medigap policy without medical underwriting?
In most cases, yes. Losing group health coverage from an employer opens a one-time guaranteed issue right for a Medigap supplement policy, typically within 63 days of the employer coverage ending, meaning insurers cannot deny you or charge more based on health conditions.
