Can I apply for Part B before my employer coverage actually ends?

Yes. You can apply for Part B up to 3 months before your planned retirement or coverage end date, and request a future effective date. Social Security will process the application and Part B will take effect on the date you specified (usually the first of the month after your employer coverage ends). This avoids any gap in coverage.

Does my employer have to complete Form CMS-L564?

Yes, but they're required by Medicare regulations to do so when an enrollee requests it. Some HR departments aren't familiar with the form because it doesn't come up often. If you encounter resistance, point to the form's instructions or contact your employer's benefits department directly. If your employer has been acquired, merged, or closed, you may need to obtain employment records from successor entities or document creditable coverage through pay stubs, plan documents, and tax records.

What if I worked for multiple employers past 65?

Each employer that provided creditable coverage during your delay period should complete a separate Form CMS-L564. Submit all of them together with your Part B application. The dates of coverage across the forms should show no significant gaps — if there were gaps in creditable coverage, those months may count toward a late-enrollment penalty.

Can I use the SEP if I retired but my spouse is still working with active coverage that covers me?

Yes, but the SEP starts when YOUR spouse's coverage of you ends, not when you personally retired. If you're a dependent on your spouse's active employer plan and your spouse keeps working, you can delay Part B as long as your spouse's coverage continues. When your spouse retires (or you lose dependent eligibility for any reason), your 8-month SEP begins.

Does the SEP apply to disability Medicare or only age 65+ Medicare?

The SEP applies to both. Anyone enrolled in Medicare due to disability who continues to have active employer GHP coverage (theirs or a spouse's) can delay Part B and use the SEP after that coverage ends. The 20-employee rule changes for disabled enrollees — it's 100 employees rather than 20 for the GHP to be primary. Check with your employer about Medicare Secondary Payer status.

Will the late-enrollment penalty go away if I become eligible for Extra Help?

No, the Part B late-enrollment penalty is separate from the Part D Extra Help program. Extra Help can reduce or eliminate Part D late-enrollment penalties for low-income beneficiaries, but it doesn't affect Part B. The only way to remove a Part B late-enrollment penalty is through the Equitable Relief process, available only in specific circumstances (typically when Medicare or your employer gave you incorrect information that led to the delay).

Medicare Part B Special Enrollment Period: 8 Months and Form CMS-L564

On this page

When the 8-month clock starts
Form CMS-40B and Form CMS-L564
How to apply for Part B during the SEP
Effective dates and timing
If COBRA is your only coverage
What to do if you missed your SEP
Part D after the Part B SEP
Common questions

When the 8-month clock starts

The Part B Special Enrollment Period begins on the date after the earlier of these two events:

The day your active employment ends (your retirement date, your last day of work, your termination date).
The day your active employer-sponsored health coverage ends.

Usually these are the same date, or close to it. But not always — some employers extend health coverage to the end of the month of retirement, while employment ended mid-month. The earlier of the two starts your clock. Conservatively, count from your last day of work.

You have 8 calendar months from that start date to enroll in Part B without a late-enrollment penalty. Apply early in the window when possible — there's no benefit to waiting.

The COBRA mistake (worth repeating)

COBRA continuation coverage does NOT extend your SEP. Your 8-month clock starts when active employer coverage ends, not when COBRA ends. If you elect 18 months of COBRA and wait to enroll in Part B until COBRA ends, you've used up your SEP plus 10 additional months — and the late-enrollment penalty applies for life. If you go on COBRA, plan to enroll in Part B within 8 months of your last active-employment date, not 8 months after COBRA ends.

Form CMS-40B and Form CMS-L564

Two forms are involved in a Part B SEP enrollment:

Form CMS-40B — Application for Enrollment in Part B. This is your application. You fill it out, sign it, and submit it to Social Security. Available at SSA.gov or your local SSA office.
Form CMS-L564 — Request for Employment Information. This is the form your employer (or former employer) completes to verify that you had active employer health coverage past 65 and the dates of that coverage. Your employer's HR or benefits administrator must complete and sign this form.

Section A of CMS-L564 is filled out by you. Section B is completed by your employer — they verify your employment dates and your enrollment in their group health plan. Most large Ohio employers (Cleveland Clinic, OSU, Procter & Gamble, Nationwide, AEP, FEHB agencies) have HR processes for this and can turn it around in a few business days. Smaller employers may need a nudge.

Submit both forms together to your local Social Security office, by mail, or by uploading through your my Social Security online account. SSA processes the Part B enrollment and notifies Medicare.

How to apply for Part B during the SEP

Three ways to apply:

Online through your my Social Security account at ssa.gov/medicare/sign-up. You can complete CMS-40B and upload CMS-L564 electronically.
By mail — print CMS-40B and CMS-L564, complete them, and mail to your local Social Security office.
In person at any Social Security office. Bring both forms (with the employer section of CMS-L564 already completed) and your Medicare card if you have Part A.

If you're already enrolled in Part A and just adding Part B during the SEP, the process is simpler — Social Security has your record on file. You just need CMS-40B plus the employment verification on CMS-L564.

Need help timing your Part B enrollment around retirement?A licensed Ohio Medicare agent can walk you through the CMS-40B and CMS-L564 paperwork, time the application around your retirement date, and help you select Medigap or Medicare Advantage coverage to start the same date Part B becomes effective.

Find a Medicare Agent in Ohio

Effective dates and timing

Part B coverage during an SEP becomes effective the first day of the month after you submit your completed application to Social Security. If you apply during the same month your employer coverage ends, you can request coverage to begin the day after employer coverage ends to avoid a gap.

Examples:

Employer coverage ends May 31, 2026. Apply for Part B in June 2026. Part B coverage effective July 1, 2026. There's a one-day gap on June 1 (often manageable with COBRA bridge coverage or careful timing).
Employer coverage ends May 31, 2026. Apply for Part B during May, requesting June 1 effective date. Part B coverage effective June 1, 2026. No gap.
Employer coverage ended February 28, 2026. Apply for Part B in September 2026 (still within the 8-month SEP). Part B coverage effective October 1, 2026. Six-month gap unless you had COBRA or other bridge.

Most retiring Ohioans apply for Part B in the month before or the month of their retirement to minimize coverage gaps. Coordinate with your Medigap or Medicare Advantage enrollment so both start the same date.

If COBRA is your only coverage

If you elected COBRA after retiring, your Part B SEP clock has already been running since the day active employer coverage ended (typically your retirement date). Don't wait until COBRA ends to apply for Part B — you'll miss the SEP.

The recommended approach if you're on COBRA past 65:

Apply for Part B during the SEP (within 8 months of when active employer coverage ended).
Decide whether to keep COBRA running alongside Part B. COBRA may pay for things Medicare doesn't, but COBRA premiums are typically expensive (102% of full plan cost, including the employer share).
Most retirees drop COBRA once Part B is effective and either enroll in a Medigap or Medicare Advantage plan — the combination usually costs less than COBRA and provides better long-term coverage.

One exception: if you have a young dependent on COBRA and they're not Medicare-eligible, you may need to keep COBRA running for them while you transition to Medicare. The premium structure changes; consult with HR.

What to do if you missed your SEP

If your SEP closed without you enrolling in Part B:

Enroll during the General Enrollment Period (January 1 – March 31 each year). Coverage starts the month after enrollment.
Pay the late-enrollment penalty. The penalty is 10% of the Part B premium for each 12-month period you went without Part B after first becoming eligible. The penalty stays with you for life.
Request a penalty waiver if you have legitimate creditable coverage documentation. If you can prove that you had active employer GHP coverage during the delay period — Form CMS-L564 from each relevant employer, MSP notices, plan documents — you can ask Social Security to recalculate. The Equitable Relief process applies if Medicare gave you incorrect information that led to the delay.

If you've missed the SEP and the General Enrollment Period is months away, you'll go without Part B coverage in the meantime. Original Medicare's Part A still covers hospital stays. For outpatient and doctor visits, you'd pay full price out of pocket until Part B begins.

Part D after the Part B SEP

If you also delayed Part D drug coverage because of creditable employer prescription coverage, you have a separate 2-month SEP for Part D when your employer drug coverage ends. See our Part D Creditable Coverage guide for that process.

Part D enrollment isn't strictly linked to Part B enrollment — you can enroll in Part D as a stand-alone PDP whether or not you have Part B. But if you're choosing a Medicare Advantage plan that includes drug coverage, you'll need both Parts A and B first.