Retiring at 70 with employer coverage means you can enroll in Medicare Part B penalty-free through a Special Enrollment Period — but only if you act within the 8-month window that starts the month your work (or your group coverage) ends. Miss that window, and you fall into the General Enrollment Period and face a permanent 10% Part B late-enrollment penalty for each 12-month period you were uncovered (Forbes).
Here's the good news: you don't need to enroll just because you turned 65. As long as you stayed on active group health insurance through an employer, Medicare lets you delay Part B without penalty and pick it up when you retire. The path is straightforward once you understand the window, the forms, and the proof of coverage the Social Security Administration (SSA) expects.
The Initial Enrollment Period versus the Special Enrollment Period
When you turned 65, Medicare opened a seven-month Initial Enrollment Period — three months before your birthday month, your birthday month itself, and three months after. Most people sign up for Part B then. But you have a legal reason not to: while you're still on active group coverage through an employer, you can keep your group plan and delay Part B without any penalty.
The trade-off is that delay duty flips to you. Once you retire, the standard sign-up path no longer applies. You must use the Special Enrollment Period (SEP), which opens the month your employment-based coverage ends and stays open for a total of 8 months. Sign up within that window and you get Part B with no late penalty. Let it lapse, and you drop into the General Enrollment Period, where the 10% penalty starts to accrue.
Prerequisites: your retirement and coverage-end dates, your Social Security number, help from your employer's HR or benefits team, and about 30 minutes. Cost for the form is free — the standard Part B premium applies once you're enrolled.
Step 1: Enroll online through Social Security
When you're 65 or older, you can enroll online for Parts A and B through the Social Security Administration (SSA). Go to ssa.gov, select "Sign up for Medicare," and follow the Part B application. The online path is the fastest route and gives you an immediate confirmation of submission.
Prefer another way? You can also call SSA at 1-800-772-1213, or make an appointment at a local Social Security office (SSA). Every route asks for the same basics: your personal details, your health insurance information, and proof of the coverage you're leaving.
Success check: You should receive a confirmation number or written acknowledgment that your Part B application was received.
Step 2: Get your employer to verify your coverage
Here is the paperwork that trips most retirees up. To use the SEP and skip the penalty, you must prove you had creditable employer group coverage from age 65 onward. SSA handles that proof with two forms: Form CMS-40B (your Part B application) and Form CMS-L564 (the request for employment information) your employer completes.
In practice, your HR or benefits administrator fills out and signs CMS-L564, confirming the dates you were covered under the group plan. That signature is what tells Social Security you were legitimately allowed to delay Part B — and what shields you from the late penalty. Submit CMS-L564 with your CMS-40B application. If your employer balks at filling it out, SSA can sometimes contact them directly, but you get the fastest result by hand-carrying the form yourself.
Success check: Your employer has completed and signed CMS-L564, and you've attached it to your Part B application.
Pro tip: COBRA continuation coverage and retiree health plans do NOT extend your Special Enrollment Period. The 8-month SEP clock starts the moment your active group coverage ends — keep COBRA while you decide, but begin your Part B application right away so you don't fall into the penalty.
What happens if you miss the 8-month window
If you miss the SEP and file later, you're pushed into the General Enrollment Period (GEP), which runs January through March each year, with coverage starting July 1. Worse, the penalty shows up and it never leaves. For every full 12-month period you were eligible for Part B but didn't enroll, your monthly premium permanently increases by 10% (Forbes).
A two-year delay, for example, adds a 20% surcharge on top of your Part B premium for life. That's not a one-time fine — it compounds against the 2026 standard premium month after month as long as you keep Medicare. This is the single most avoidable retirement cost, and the only true defense is filing within your SEP with CMS-L564 in hand.
Troubleshooting common snags
Getting stuck? Here's how to resolve the scenarios that derail most retirements:
1My employer won't fill out CMS-L564. What now?
Tell Social Security about the delay when you submit CMS-40B. SSA can contact your employer directly to verify the coverage dates, which keeps you inside the SEP. You still must file before the 8-month window closes.
2Does COBRA extend my 8-month Special Enrollment Period?
No. COBRA continuation and retiree health plans trigger the SEP clock the moment employment-based coverage ends. You may keep COBRA while deciding, but start your Part B application immediately to stay penalty-free.
3I missed the SEP and now I pay the late penalty. Can it be removed?
The Part B late penalty is permanent once applied, and it is added to your monthly premium for as long as you have Medicare. Your only lever is to enroll as soon as possible so the surcharge doesn't grow with each additional 12-month gap.
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