If you are turning 65 while still working, or leaving a job at 65 or older, Part B has its own clock and its own paperwork. Getting it wrong carries a penalty that is added to your premium for life. This checklist covers the deadline, the two forms, and the mistake that causes the most damage.
It is written to be printed and worked through with your employer’s benefits administrator.
Do I have to take Part B at 65 if I am still working?
Usually not, if your coverage comes from current employment at a large employer. That situation lets you delay Part B without a penalty and pick it up later through a Special Enrollment Period.
But there is a size threshold that catches people out. If the employer has fewer than 20 employees, Medicare generally becomes the primary payer once you are eligible, and the group plan may pay little or nothing until you enroll. Delaying in that situation can leave you effectively uncovered while believing you are insured. Ask the benefits administrator one direct question — does this plan pay primary or secondary once I turn 65? — and get the answer in writing.
What is the mistake that causes the most damage?
COBRA is not group health plan coverage for this purpose, and taking it does not extend your Part B window. Neither does retiree coverage. Both feel like continuing coverage, and neither stops the clock.
Your Special Enrollment Period ends 8 months after your group health coverage ends or your employment ends — whichever happens first. Someone who leaves a job, elects COBRA for 18 months, and then goes looking for Medicare has usually missed the window by ten months, and will face both a gap and a permanent penalty.
If you have been offered COBRA and you are 65 or older, treat the Part B decision as urgent and separate. Losing job health coverage covers the rest of that decision.
How long do I actually have?
- Starts: the first month after your Initial Enrollment Period ends.
- Ends: 8 months after your group health plan coverage ends or your employment ends, whichever comes first.
- Coverage begins: generally the first month after you sign up.
- A provision worth knowing: if you sign up while you or your spouse are still working, or within the first full month after the employer coverage ends, you can ask to delay your Part B start date by up to 3 months. That is how you line Part B up with the end of the employer plan instead of paying for both.
This Special Enrollment Period does not apply if you are eligible for Medicare because of End-Stage Renal Disease, or if you are still inside your Initial Enrollment Period.
The two forms
Signing up through this window is not the same as signing up at 65, and it is the step people assume will happen automatically. It does not.
- CMS-40B — Application for Enrollment in Part B. You complete this one. If you already have Part A, you can apply online at ssa.gov instead.
- CMS-L564 — Request for Employment Information. Your employer completes this one. It is Social Security’s proof that you had coverage through current employment after turning 65, and it is what protects you from the penalty.
Start the L564 early. It has to travel through someone else’s HR department, and that is where these applications stall. If the employer no longer exists or will not complete it, that is a solvable problem — Social Security accepts other proof, such as pay stubs showing health premiums, W-2s, or written statements — but it takes longer, so find out early rather than in month seven.
Before you drop the employer plan
- Confirm your Part B start date in writing before you cancel anything. Do not let the old coverage end before the new coverage begins.
- Decide the rest of the picture too. Part B on its own leaves a share of costs uncapped. A supplement or an Advantage plan and drug coverage are separate decisions with their own deadlines, and the supplement one is the least forgiving in Georgia.
- Check drug coverage specifically. If your employer plan’s drug coverage was not creditable, a separate late penalty can apply to Part D. Ask the benefits administrator whether it was — they know the term.
- If your spouse is on your plan, work out what happens to them the day it ends. This is the piece most often discovered last.
If you have a Health Savings Account, read this part twice
You cannot contribute to an HSA once you are enrolled in any part of Medicare. The complication is that Part A can be backdated up to 6 months when you enroll after 65, so contributions made during those retroactive months can become excess contributions with a tax consequence attached.
The practical rule most people need: stop HSA contributions roughly six months before you plan to enroll. Whether that applies to you, and what to do if contributions have already been made, is a question for whoever prepares your taxes. I am an insurance agent — my job here is to make sure the question gets asked in time, not to answer it.
What if I already missed the window?
You would sign up during the General Enrollment Period, January 1 to March 31, with coverage starting the month after you sign up. A late enrollment penalty is typically added to your Part B premium for as long as you have it.
It is still worth asking rather than assuming. Penalties are sometimes reversed when the delay was caused by bad information from an employer or a federal employee, and there is a process for requesting that. It is not automatic and it is not guaranteed, but people who never ask never get it.
The order to work in
Ask the benefits administrator whether the plan pays primary or secondary at 65, and whether its drug coverage is creditable. Find your exact last day of coverage. Get the L564 to HR early. Submit both forms, and ask for the start date that lines up with your coverage ending. Confirm the start date in writing. Only then cancel the old plan.
Common questions
Will Social Security enroll me automatically?
Only if you are already receiving Social Security benefits when you become eligible. If you delayed benefits — which many people working past 65 have — nothing happens automatically and the application is yours to file.
Does my employer tell me when to do this?
Some do it well and some do not mention it. It is not their obligation to track your Medicare deadlines, and “nobody told me” is unfortunately not a defense that removes a penalty.
Can I delay Part B if I am covered by my spouse’s employer plan?
Generally yes, on the same terms, provided it is coverage through their current employment and the employer is large enough. The same size question applies.
What does it cost to get help with this?
Nothing. There is no cost for the guidance, and it does not change what you pay for any coverage.
Want a second pair of eyes on the timing?
This is the part of Medicare with the least room for error and the least helpful paperwork, and it is worth an hour with someone who has done it before. Call or text 770-765-7007, or pick a time. The enrollment calculator will give you your dates, and Medicare and employer coverage covers the wider decision. We are in Cumming, Georgia, and work with households across North Georgia: Forsyth, Cherokee, Hall, Dawson, Lumpkin, Pickens, Gilmer, Fannin, Union and White counties, plus north Gwinnett and north Fulton.
Enrollment periods, coverage start dates and form numbers on this page come from Medicare and the Social Security Administration directly. Figures that reset each January are deliberately left off.