CMS-40B and CMS-L564: How New York Residents Enroll in Medicare Part B After Employer Coverage

If you worked past 65 in New York and stayed on your employer's health plan, Social Security is not going to hand you Part B when you retire. You have to ask for it in writing, using two forms: CMS-40B and CMS-L564.

File them correctly and Part B starts on the date you picked, with no penalty. File them late, or leave the wrong box blank, and you can end up paying a surcharge on your premium every month for as long as you have Medicare.

Here is what each form does, who fills out which section, and the timing that trips people up.

The two forms and what each one proves

They travel together. One is your application. The other is your alibi.

• CMS-40B, Application for Enrollment in Medicare Part B. This is you telling Social Security you want Part B and when you want it to start. If Medicare is still new to you, our beginner's guide to Medicare coverage options covers how the parts fit together. You fill out the whole thing.
• CMS-L564, Request for Employment Information. This is your employer confirming you had group health coverage based on current employment after you turned 65. That confirmation is what erases the late enrollment penalty.

Neither of these comes up in the standard turning 65 enrollment checklist, because that path assumes you are leaving work on schedule. Neither form is New York-specific. They are federal forms handled by the Social Security Administration, so a NY resident files the same paperwork as someone in any other state. What changes locally is where you send them and how long your regional office takes to process them.

CMS-40B: the part everyone rushes

The form itself is one page. Name, Medicare number (you already have one if you took Part A at 65), signature, date.

The box that actually matters is Remarks. That is where you write the month you want Part B to begin. Something like:

I want Part B coverage to begin 07/01/2026.

Leave it blank and Social Security picks for you, usually the month after they process the application. If your employer coverage ends June 30 and Part B does not start until August, you have a gap with no coverage and no Medigap clock running.

One wrinkle worth checking first: if you were still contributing to a health savings account through the New York job, Medicare enrollment shuts down HSA contributions six months retroactively. If your group coverage has already ended, add a second line saying you had group health plan coverage based on current employment after age 65. Redundant with the L564, and worth writing anyway.

Want a wider look at the program you are buying into? Our guide to what Part B covers and what it costs walks through the premium, the deductible, and the 20% coinsurance you will be responsible for, and our breakdown of what Medicare costs in 2026 puts those numbers next to everything else you will owe.

CMS-L564: the form your HR department has to touch

Section A is yours. Section B belongs to the employer. They confirm the dates the plan was in force and, critically, whether the coverage was based on current employment.

"If you didn't take Medicare because you had employer benefits, you need to complete two forms and submit them to Social Security," says Mark Bilgere, a licensed Medicare agent in Bedford, Texas. "You must have your employer complete the CMS-L564 acknowledging you had creditable coverage since you turned 65."

Two details people miss.

First, the employer has to be the one whose plan actually covered you. If your coverage came through a spouse's job, it is the spouse's HR department signing, not yours.

Second, you need one L564 per employer. Changed jobs at 68 and again at 70? That is three forms, and every month between age 65 and your Part B start date has to be accounted for. A gap in the paper trail is a gap Social Security can penalize.

The size of the employer matters too. The 20-employee threshold decides whether Medicare or the group plan pays first, and it is the rule behind most of the bad advice people get from coworkers. We break it down in our piece on Medicare and employer coverage past 65.

What if the employer is gone or won't sign

Companies get acquired. HR departments lose records. Small employers sometimes just stop answering.

Social Security will accept secondary proof instead of a completed Section B:

• W-2 forms showing pre-tax health insurance contributions
• Pay stubs with health premium deductions
• Insurance cards showing effective dates
• A written statement from the insurance carrier or plan administrator
• Old enrollment or open enrollment confirmations

Attach what you have, and use the Remarks box on the 40B to explain why Section B is blank. Claims reps deal with this constantly. They are not looking for a reason to say no, but they do need something in the file.

The 8-month window, and the trap inside it

Your Part B Special Enrollment Period runs 8 months, starting the month after your employment ends or the month after the group coverage ends, whichever happens first.

Now the trap. COBRA and retiree coverage do not count as current employment. If you retire in March, take COBRA for 18 months, and then try to enroll in Part B, your SEP expired back in November. You are stuck waiting for the General Enrollment Period, and the Part B late enrollment penalty follows you permanently at 10% for every full 12 months you could have had Part B and didn't. It is only one of several Medicare penalties that outlast the mistake that caused them.

The eight months is an outer limit, not a target. Agents push clients to start earlier, because employer HR departments move slowly and Social Security processing is not instant.

"Typically, what I tell my clients is that this needs to be done at least 2 months before your retirement or when your creditable coverage from your employer ends," says Diana Pedersen, a licensed Medicare agent in Mead, Washington.

Two to three months of lead time is realistic if you want Part B live the day your New York group plan shuts off. For a fuller map of which enrollment window applies to your situation, see our guide to Medicare Special Enrollment Periods.

Where to send the forms

You have four options as a New York resident, and they are not equally good:

1. Upload online at ssa.gov. Fastest, and you get a confirmation receipt. Use this one.
2. Fax to your local Social Security office. Works, but keep the transmission report.
3. Mail. Send it certified. Paper gets lost.
4. In person at a field office. Appointments book out weeks in many areas, so only plan on this if you have time.

Whatever route you take, photograph or scan both completed forms before they leave your hands. If the file goes missing you will be asked to produce them again, and chasing a former employer twice is miserable.

Our step-by-step on how to apply for Medicare covers the rest of the application process if you are also enrolling in Part A at the same time.

What happens after you file

Social Security mails a confirmation, then a new Medicare card showing both Part A and Part B effective dates. Give it 3 to 6 weeks, longer during the fall.

Two clocks start the day Part B takes effect:

• A 6-month Medigap open enrollment period, the one stretch where no insurer in New York can turn you down or price you up for health history. It sits alongside the narrower guaranteed issue rights and the other Medigap enrollment windows.
• A 63-day window to pick up a Part D drug plan or a Medicare Advantage plan before the Part D late enrollment penalty starts accruing.

The Medigap window is the one people waste. Six months, no medical underwriting, and it never comes back.

Mistakes that cost real money

These overlap with the broader list of mistakes first-time enrollees make, but the employer-coverage crowd has its own set.

• Leaving Remarks blank on the 40B. You lose control of your start date.
• Counting COBRA as employer coverage. The single most expensive misread on this page.
• Submitting one L564 for multiple jobs. Every employer since 65 needs its own.
• Waiting for HR to "get around to it." Ask in writing, give a deadline, follow up weekly.
• Assuming Part A enrollment covers you. Part A is hospital coverage. Doctor visits, labs, imaging, and outpatient surgery are all Part B.
• Paying the full premium when you don't have to. If retirement drops your income, Extra Help and the low income subsidy can cut what you owe.

None of this is hard. It is just unforgiving about timing. If you want a second set of eyes before you send anything in, a licensed agent in New York will walk through the forms with you at no cost, and most of them have filed hundreds of these. And if retirement also means relocating, read up on how moving changes your Medicare plan before you pick coverage.