What is form CMS-L564?

CMS-L564, Medicare Request for Employment Information, is the form an employer completes to confirm you had group health plan coverage based on current employment. You complete Section A; your employer completes Section B. It is submitted with CMS-40B to enrol in Part B through a Special Enrollment Period.

Who fills out CMS-L564?

Both of you. You complete Section A with your details and your employer’s name and address. The employer, or its HR or benefits administrator, completes Section B with the employment and coverage dates, and a company official signs it. You cannot complete it alone.

How long do I have to use a Special Enrollment Period?

The form states it directly: your group health plan coverage must not have ended more than 8 months ago, and you must have had that coverage through your or your spouse's current employment since the first month you were eligible for Part B.

Late enrolment penalties

CMS-L564: proving you had employer coverage

If you stayed on an employer’s health plan past 65 and delayed Medicare Part B, this is the form that proves it. You fill in half of it; your employer fills in the rest — and that second half is where this goes wrong.

Checked against CMS-L564 (Revised 03/2025, OMB 0938-0787, expires 03/2028) and CMS-40B (07/2025, OMB 0938-1230). Download both from CMS or SSA, not a third-party form site.

The 8-month rule, from the form itself

CMS-L564, page 1

“To enroll in Medicare through a Special Enrollment Period, you must have had group health plan coverage through your or your spouse's current employment since the first month you were eligible for Medicare Part B. Your coverage must not have ended more than 8 months ago.”

Two conditions, and both matter. The coverage has to have been continuous since the first month you were eligible for Part B — a gap breaks it. And the eight months run from when the coverage ended, not from when you noticed.

If you qualify for Medicare because of a disability, you must have large group health plan coverage based on your, your spouse's or a family member's current employment.

Who fills in what

You — Section A

Applicant's name and Social Security Number; Employee's name and SSN, if different from the applicant; Employer's name and full address. The separate 'employee' fields are how the spouse case works: if your coverage came through your spouse's job, you are the applicant and your spouse is the employee.

Your employer — Section B

The employer, or its HR or benefits administrator answers when coverage started, whether and when it ended, the employment dates, and whether you are still employed. Signature, printed title and phone number of a company official, plus the date signed. You cannot fill this in yourself.

The part that actually stalls

CMS estimates the form takes 15 minutes. That is the typing. Getting Section B signed is the real task — and if the employer has been acquired, has outsourced its benefits administration, or no longer exists, it can take weeks. The eight-month clock does not pause while you look. Start with Section B, not last.

Three things buried in these forms

You can choose when Part B starts. If you're enrolling in Medicare while you're still covered by a group health plan based on current employment (or during the first full month you're not enrolled in the group health plan), you can choose when your Medicare coverage will start. The options are: The first day of the month you enroll, or The first day of any of the 3 months after you enroll. This is on CMS-40B and is easy to miss. It lets you line up the Medicare start date with the end of employer coverage, instead of paying two premiums for overlapping months.

Hours Bank Arrangements have their own section. The form carries a section for Hours Bank Arrangements — common in union and trade plans, where banked hours keep coverage running after work stops. If that is your situation, the date your reserve hours run out matters as much as your last day of work.

There is a question about being pushed onto Medicare. CMS-40B asks whether an employer, insurer or other entity asked or required you to enrol in Part B, and tells you to explain and attach proof if so. Worth answering carefully: it exists because pressuring someone off a group plan and onto Medicare is not always permitted.

CMS-40B also asks whether you were an international volunteer for a non-profit that provided your health coverage — a separate route to a Special Enrollment Period that almost nothing written about this form mentions.

Sending them in

“Mail or fax this completed form together with your Application for Enrollment in Medicare (CMS-40B) to your local Social Security office.” Find yours with the SSA office locator. Neither form offers an online submission route. Mail or fax only.

The two forms travel together: CMS-40B is the actual Part B application, CMS-L564 is the evidence that you may apply late. And a trap on the application itself — “If you don't have Part A, don't complete this application. Contact Social Security to apply for Medicare for the first time.”

CMS-40B covers three enrolment windows: Initial Enrollment Period; General Enrollment Period from January 1–March 31 each year; If you're eligible for a Special Enrollment Period.

Free, unbiased help

Both forms point to the State Health Insurance Assistance Program for free, personalised and unbiased counselling — the forms' own word is 'unbiased', which is more than can be said for most help offered on this subject. Find your local counsellor at shiphelp.org, or call Social Security on 1-800-772-1213 (TTY 1-800-325-0778). Call the same number and press 2 for service in Spanish.

What we are not telling you

Neither CMS-L564 nor CMS-40B states the Part B late-enrolment penalty formula. We are not publishing a figure for it until it is checked against CMS or SSA directly. It is the figure most pages lead with, and it appears on neither form — so we have left it out rather than repeat what everyone else says. Why we work this way.

What we can say is why it matters: the Part B late enrolment penalty is added to your premium for as long as you hold Part B, and it is calculated from the standard premium — $202.90 a month in 2026 — so it rises whenever that does.

How this relates to IRMAA

Different problem, same premium. IRMAA is a surcharge based on your income two years ago; the late enrolment penalty is a surcharge based on when you signed up. Both are added to the same Part B bill, and someone who worked past 65 on a good salary can end up paying both.

If that is you, the 2026 IRMAA brackets show the income side, how IRMAA works explains why the year that matters is already behind you, and what each threshold costs shows whether it is worth managing.