By Christian BrinkleyLicensed NC Insurance Agent, NPN 22217190, NC Life & Health · Updated October 10, 2026 · 3 min read
Turning 65 while you are still working is one of the most common situations I hear about, and the answer surprises people. You do not always have to enroll in Medicare at 65. If you have health coverage through your or your spouse's current job, and the employer has 20 or more employees, you can usually delay Part B with no penalty. When that job coverage ends, you get an 8-month Special Enrollment Period. But the details matter, and one mistake, contributing to a Health Savings Account while on Medicare, costs people real money every year.
The 20-employee rule
Everything turns on the size of the employer. If the company has 20 or more employees, its group health plan pays first and Medicare pays second. That arrangement counts as creditable coverage, and it lets you delay Part B without a penalty. If the employer has fewer than 20 employees, Medicare pays first, which means you should enroll in Parts A and B at 65 even while working.
Check with your benefits office if you are not sure how many employees count. Large employers sometimes have small subsidiaries, so confirm the number for the actual employing entity, not the parent company.
Part A: usually take it, with one exception
Part A is premium-free for almost everyone based on work history, so most people sign up at 65 even while working. It costs nothing and sits in the background as secondary coverage. The exception: if you are contributing to a Health Savings Account. You cannot contribute to an HSA once you are enrolled in any part of Medicare, including premium-free Part A.
People get caught by this every year. If you want to keep funding your HSA, delay all of Medicare, including Part A, until you retire. You can still spend what is already in the HSA, you just cannot add to it.
The 8-month Special Enrollment Period
When your job-based coverage ends, whether you retire or switch jobs, you get an 8-month Special Enrollment Period to sign up for Part B with no late penalty. The clock starts the month after employment or coverage ends, whichever comes first.
Eight months sounds generous until life gets busy. Mark the date the day your coverage ends. Miss the window and you wait for the General Enrollment Period like everyone else, penalty included.
What does not count: COBRA and marketplace plans
This is where people get hurt. COBRA continuation coverage does not qualify you for a Special Enrollment Period, even though it feels like employer coverage. Marketplace plans do not count either. If you retire at 66, take COBRA for 18 months, and then try to sign up for Part B, Medicare treats you as if you had no coverage.
You owe the penalty and you wait for January. If you are leaving a job, sign up for Medicare during your Special Enrollment Period instead of riding out COBRA.
Drug coverage while you work
Your employer's drug coverage needs to be creditable too, or you face the Part D late penalty later. Each fall your plan must send a notice saying whether its drug coverage counts. Keep that letter. If you ever need to prove you had coverage, it is your proof.
If you are unsure, ask your benefits office directly: is our prescription drug coverage creditable for Medicare Part D purposes? Get the answer in writing.
Questions people ask me about this
Can I keep contributing to my HSA if I enroll in Medicare Part A?
No. Once you enroll in any part of Medicare, including premium-free Part A, you must stop contributing to your HSA. You can still spend what is already in it.
Does my spouse's small employer plan let me delay Medicare?
Only if the employer has 20 or more employees. With a smaller employer, Medicare pays first and you should enroll in Parts A and B at 65.
What happens to my employer coverage when I turn 65?
Nothing automatic. Your employer plan continues as normal. You choose whether to add Medicare based on the 20-employee rule and your costs.
I retired but my spouse still works. Can I use their plan?
Yes, if it comes from your spouse's current employment with 20 or more employees. The same payer-order rules apply as if it were your own job.
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