Medicare Part B Special Enrollment After Employer Coverage Ends: A Family Guide to CMS-40B and CMS-L564

Educational note: This guide offers general information for older adults, spouses, adult children, caregivers, and family helpers. It is not legal, medical, financial, tax, or insurance advice. Medicare eligibility and coordination can depend on the person, the employer plan, the reason for Medicare eligibility, and the timing of employment and coverage. Confirm important dates with Social Security, Medicare, and the employer benefits administrator.

The calendar matters twice when employer health coverage is ending: once for the last day of work, and again for the last day of coverage. Those dates may be different, and the earlier one can start the Medicare Part B Special Enrollment Period clock. A retirement celebration or COBRA election does not pause that clock. The safest approach is to build the enrollment file before the employer plan ends, request the employment form early, and keep proof of every submission.

This guide focuses on people who delayed Medicare Part B because they had group health plan coverage based on their own or a spouse's current employment. It explains how to organize Form CMS-40B, Form CMS-L564, coverage dates, employer verification, and follow-up without trying to decide whether any individual should enroll or which coverage is best.

The core rule: current employment is what matters

Medicare says that, after the Initial Enrollment Period, a person with qualifying job-based coverage may generally sign up for Part B while the worker is still employed or during the eight months after the employment or group health plan coverage ends, whichever happens first. The official Medicare coverage-start and Special Enrollment Period page also explains that this opportunity is limited and that coverage generally begins the month after enrollment.

The phrase based on current employment is the important filter. Coverage may come through the older adult's job or a spouse's job. For a person entitled to Medicare because of disability, qualifying coverage may in some circumstances come through a family member's current employment and a large group health plan. Because those rules are more specific, confirm the situation directly with Social Security.

Do not assume that any insurance card from an employer or former employer creates the same enrollment protection. Medicare identifies COBRA and retiree coverage as situations that do not count as group health plan coverage based on current employment for this Part B Special Enrollment Period. Marketplace coverage also follows different rules.

Why COBRA does not reset the Part B deadline

COBRA can be valuable because it may temporarily continue an employer plan after employment or work hours end. But it does not extend the eight-month Part B enrollment window. Medicare's COBRA coverage guidance says the Part B period runs from when work stops or health insurance is lost, whichever happens first, whether or not COBRA is elected.

The COBRA decision also affects family members differently. A spouse or dependent may need continuation coverage even if the Medicare-eligible worker moves to Medicare. The U.S. Department of Labor's COBRA questions and answers describes several Medicare and COBRA sequences and warns that coordination can change depending on which enrollment happened first. Before making changes, ask the employer plan how coverage will work for the worker, spouse, and dependents separately.

Start with a two-date timeline

Write down these dates before filling out a form:

• Employment end date: the last day the covered employee is working, not the retirement-party date or the final paycheck date.
• Employer group coverage end date: the last day the active-employee plan covers the Medicare applicant.

If employment ends June 14 but active coverage continues through June 30, the employment date comes first. If coverage ends May 31 while the employee remains on payroll through June, the coverage date comes first. Medicare's rule uses whichever event happens first. A family organizer should circle that earlier event, record how it was confirmed, and avoid treating the eighth month as the target. Filing earlier creates time to resolve missing employer records or processing questions.

For a smoother handoff, Medicare advises people who want Part B to begin when job-based insurance ends to sign up about a month before retirement or coverage loss. Start-date choices can depend on exactly when the request is submitted. The current CMS-40B application includes coverage-start choices for people enrolling while still covered through current employment or during the first full month after that coverage ends.

The two-form enrollment packet

People who already have Medicare Part A and want to add Part B during this Special Enrollment Period commonly use two forms. Social Security's Part B-only enrollment page also offers an online route for people ending an employer group health plan.

CMS-40B: the Part B enrollment request

Form CMS-40B, Application for Enrollment in Medicare Part B (Medical Insurance), is the request to add Part B when the applicant already has Part A. Review the current form before using an old saved copy. Enter names and Medicare information consistently with Social Security records. If the form asks for employment and health-coverage dates, compare them with the employer verification rather than estimating from memory.

Pay special attention to any requested Part B start date. The goal is to coordinate the end of employer coverage and beginning of Medicare without unintentionally creating a gap or unnecessary overlap. A benefits administrator can confirm the employer plan's last active day, but Social Security processes the Medicare enrollment. When timing is unclear, ask both organizations and record their answers.

CMS-L564: proof of employment-based coverage

Form CMS-L564, Request for Employment Information, documents that the applicant had group health plan coverage based on current employment. The applicant completes Section A, and the employer normally completes and signs Section B. The CMS form page for CMS-L564 describes it as proof of group health plan coverage and directs applicants to submit it with CMS-40B to Social Security.

Send the employer a clean request that includes the applicant's name, the employee's name if different, the requested return date, and a secure return method. Ask the benefits office to verify both employment and coverage dates. If several employers provided qualifying coverage since Medicare eligibility began, Social Security may need documentation for more than one period.

If the employer will not or cannot complete CMS-L564

A closed business, merger, outsourced benefits office, or old payroll system can make employer verification difficult. Do not wait silently for weeks. Medicare's Part A and Part B sign-up instructions say that if the employer cannot complete CMS-L564, the applicant can complete Section B as best they can but should not sign that section, and should submit proof of job-based insurance.

Ask Social Security which alternative documents are appropriate for the case. Possible records may include:

• health insurance cards showing effective dates;
• premium statements, pay stubs, or employer records showing health deductions;
• tax forms or wage statements that help establish employment;
• coverage letters from the insurer or plan administrator;
• COBRA election materials that identify when active employment coverage ended; and
• dated correspondence documenting attempts to obtain the employer's signature.

These examples are preparation ideas, not a promise that a particular document will be accepted. Keep originals unless an agency specifically requests them, and send copies through an approved secure method.

A family packet that another person can understand

Create one paper or encrypted digital folder with a simple cover sheet. Avoid placing Social Security numbers, Medicare numbers, or medical details in ordinary email, shared notes, or text messages.

Packet checklist

• A one-page timeline listing Medicare eligibility, current-employment periods, group coverage periods, retirement or employment end, and the desired transition month.
• The current CMS-40B, completed and reviewed but not altered after signing.
• The current CMS-L564, with Section A completed and Section B returned by the employer.
• Copies of employer coverage letters and the page that shows the active plan's end date.
• A list of every employer benefits contact, phone number, date contacted, and promised response date.
• A copy of the full submission exactly as sent.
• Fax confirmation, certified-mail tracking, online confirmation number, or a dated receipt from the Social Security office.
• A follow-up log with the date, representative, reference number, and next action.

If an adult child is helping, the Medicare applicant should remain involved and use Social Security's authorized processes. Knowing personal details or holding a general power of attorney does not automatically give another person unrestricted authority to transact with a federal agency.

Three decision points to resolve before submission

1. Is the coverage truly based on current employment?

Ask the benefits administrator: “Is this active-employee group health plan coverage based on the current employment of me or my spouse?” If the answer is retiree coverage, COBRA, Marketplace insurance, or another arrangement, do not assume the standard employment-based Part B window applies. Contact Social Security for the enrollment rule that matches the situation.

2. Which date ends first?

Compare employment and active group coverage. Get both dates in writing. If the employee moved to leave status, reduced hours, severance, or a retiree plan before the formal employment end, ask when coverage stopped being based on current employment.

3. What should happen to everyone else on the plan?

A Medicare enrollment decision for one person can affect a spouse or dependents. Ask whether they remain eligible for the employer plan, need COBRA, or have another enrollment opportunity. Keep their deadlines on a separate page so one person's successful Part B filing does not hide another person's coverage gap.

Practical example: retirement with end-of-month coverage

Consider Elena, who has Medicare Part A and delayed Part B while covered through her spouse Marco's active job. Marco plans to stop working September 18, and the employer confirms active coverage ends September 30. The family records both dates and treats September 18 as the earlier event. They do not plan to use the entire eight-month window.

In August, Elena completes CMS-40B and Section A of CMS-L564. Marco's benefits office completes Section B and confirms the employment and coverage dates. Elena reviews the requested Medicare start date, submits the packet through a Social Security-approved method, and saves proof. The family separately asks whether Marco or any dependent needs COBRA. Two weeks later, Elena follows up with Social Security rather than assuming delivery means processing is complete.

This example illustrates an organizing method only. It does not establish eligibility or the correct start date for another person.

After submission: verify, do not assume

A fax confirmation or online receipt proves that something was transmitted; it does not prove that Part B is active. Check the application status through Social Security, watch for mailed notices, and review the Medicare effective date when it appears. If a requested document is missing or a date is wrong, respond promptly and preserve the new submission proof.

Before the employer plan ends, also ask how prescription drug coverage, retiree coverage, Medigap, or Medicare Advantage enrollment timing may interact with the transition. Those choices have separate rules and deadlines. Free, one-on-one Medicare counseling is available through the State Health Insurance Assistance Program locator. SHIP counseling is not connected to selling a plan.

A seven-step next-action plan

1. Confirm whether coverage is tied to current employment.
2. Write down the employment end date and active group coverage end date.
3. Ask the benefits administrator how Medicare enrollment affects the worker, spouse, and dependents.
4. Download current CMS-40B and CMS-L564 forms from Medicare, CMS, or SSA.
5. Request employer completion of CMS-L564 early and document follow-up.
6. Submit through a Social Security-approved channel and save the complete packet plus proof.
7. Verify the Part B effective date and resolve any remaining coverage transitions.

The most useful family role is often not choosing the coverage. It is keeping the dates visible, making sure the employer form is moving, protecting sensitive information, and following the request until the effective date is confirmed.

Sources

• Medicare: When does Medicare coverage start?
• Medicare: Ready to sign up for Part A and Part B
• Medicare: COBRA coverage
• Social Security Administration: Sign up for Part B only
• CMS: Form CMS-40B, Application for Enrollment in Medicare Part B
• CMS: Form CMS-L564, Request for Employment Information
• U.S. Department of Labor: COBRA continuation coverage questions and answers
• SHIP Technical Assistance Center: Find local Medicare counseling