CMS-40B Form: How Federal Retirees Enroll in Medicare Part B Without Penalties

What CMS-40B Actually Is

Form CMS-40B is the official application to enroll in Medicare Part B (medical insurance). If you're a federal retiree who worked past age 65 with active FEHB coverage, this form is how you sign up for Part B during your 8-month Special Enrollment Period after separating from federal service.

The form itself is short — about two pages. But submitting it without the companion form, CMS-L564, is the mistake that costs federal retirees the most. Without L564, the Social Security Administration has no proof that you had qualifying employer-based group health coverage, and you'll be treated as someone who simply declined Part B at 65. That means a permanent late enrollment penalty: 10% added to your Part B premium for every 12-month period you were eligible but not enrolled.

The CMS-L564 Companion Form

Form CMS-L564 (Request for Employment Information) is the form your employer or former employer fills out to certify that you had active group health plan coverage based on current employment. For federal retirees, this means:

If you retired recently (within the last 8 months): Your agency's HR department completes Section B, certifying your FEHB coverage dates. Some agencies handle this through the servicing personnel office; others route it through the payroll provider.

If your agency no longer exists or HR is unresponsive: OPM can complete the CMS-L564 on your behalf. Submit a written request to OPM Retirement Services with your CSA claim number. OPM's Retirement Operations Center will verify your FEHB enrollment history from their records and certify the form.

The critical fields on CMS-L564 are the employment start and end dates and the confirmation that health coverage was based on active employment — not COBRA or retiree coverage. FEHB for active employees counts. FEHB carried into retirement does not count for SEP purposes because you're no longer actively employed — that's why the timing of your enrollment matters.

When to Submit: The 8-Month SEP Window

Federal employees who work past 65 with active FEHB coverage get an 8-month Special Enrollment Period starting from the month their employment ends (not the month their FEHB coverage ends — those are different dates if FEHB continues into retirement).

The timeline works like this:

1. You retire at age 67 in March 2026
2. Your 8-month SEP runs from March 2026 through October 2026
3. You must submit CMS-40B and CMS-L564 to your local Social Security office within that window

Coverage starts the first day of the month after the SSA processes your enrollment. There's no extra waiting period during an SEP — the General Enrollment Period also starts coverage the first of the month after you enroll, but it comes with the late-enrollment penalty.

If you miss the 8-month window, your only option is the annual General Enrollment Period (January 1 through March 31), and you'll owe the permanent 10% per-year late penalty.

How to Fill Out CMS-40B

The form asks for basic identification (name, Social Security number, Medicare claim number) and the reason you're enrolling. For federal retirees using the SEP, select the box indicating you're enrolling because you lost or are ending employer-based coverage.

Key sections:

Section 1 — Personal Information: Your name, address, date of birth, and Medicare Beneficiary Identifier (MBI) from your Medicare card. If you enrolled in Part A at 65, your MBI is already on file.

Section 2 — Employer Group Health Plan: Check the box confirming you had group health coverage through an employer. List your federal agency as the employer.

Section 3 — Coverage End Date: Enter your last day of active federal employment. This is the date that triggers the 8-month SEP clock — not your last day of FEHB coverage.

Signature: Sign and date. An unsigned form is returned without processing.

Common Mistakes That Trigger Penalties

Listing your retirement date as the coverage end date when you're carrying FEHB into retirement. The SEP is based on when your active employment ends, not when your health coverage ends. If you've been retired for three years with FEHB as retiree coverage, your SEP expired long ago.

Waiting until you're "sure" about Part B. The 8-month window is firm. If you retire at 67, spend six months deciding, and then try to file in month nine, you're past the SEP.

Submitting CMS-40B without CMS-L564. The SSA will process your enrollment, but without proof of active employer coverage, they may apply the late enrollment penalty retroactively. Getting it removed after the fact requires an appeal.

Having HR complete L564 with retiree coverage dates instead of active employment dates. The form specifically asks about coverage "based on current employment status." Retiree continuation coverage doesn't qualify — it needs to reflect the period you were actively working while enrolled in FEHB.

Where to Submit

Submit both forms together to your local Social Security office. You can:

• Mail them to the office (keep copies of everything)
• Bring them in person to a scheduled appointment
• In some cases, fax them (call first to confirm fax availability)

The SSA cannot process Part B enrollments online for SEP applicants. You must submit the physical forms. Processing typically takes 2 to 4 weeks, after which you'll receive a new Medicare card reflecting Part B coverage.

What This Means for Your FEHB Plan

Once Part B is active, your FEHB plan automatically shifts to secondary payer status for outpatient medical services. Claims go to Medicare first, and your FEHB carrier picks up whatever Medicare doesn't cover. Most major FEHB plans waive their deductibles and copayments entirely when Medicare is primary, reducing your point-of-care costs to near zero.

You don't need to notify your FEHB carrier separately — the coordination happens through the standard Medicare coordination of benefits process. However, it's worth calling your carrier to confirm how their plan handles Medicare-primary claims and whether they offer any premium reimbursement features for Part B enrollees.

For the full timeline of forms, enrollment windows, and coordination steps, the FEHB & Medicare Coordination Guide maps out the entire process from pre-retirement through Open Season planning.

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