Still on payroll at 65: how Medicare and your job fit together

At an employer with 20 or more employees, the group plan pays first and Medicare pays second. That arrangement makes the job-based plan creditable, which is what allows you to postpone Part B with no surcharge while you are working and enrolled.

Below 20 employees, the order reverses. Medicare pays first and the group plan fills in behind it, so you need both Parts A and B at 65 or the group plan will leave gaps where Medicare would have paid. Plenty of small employers require proof of enrollment for exactly that reason.

This is the table we talk through on the phone, because the exceptions matter more than the general rule.

When the job ends, or the coverage tied to it ends, eight months are available to file for Part B without a surcharge. Filing before the coverage stops avoids a gap, and benefits generally begin the first of the month after you enroll.

Those eight months belong to Part B alone. Drug coverage keeps a different clock, and 63 uncovered days can still trigger a Part D surcharge. Sort the drug plan before the final day of group coverage.

Once any part of Medicare is active, including premium-free Part A, contributions to a health savings account must stop. Since Part A often turns on automatically when Social Security begins, the practical move for someone planning to keep funding an HSA is to postpone both the Social Security claim and Part A.

Money already in the account remains yours. It can still be spent tax-free on Medicare premiums and qualified medical costs.

COBRA keeps a former employer’s plan alive. It does not count as creditable coverage for Medicare. Someone 65 or older who chooses COBRA instead of enrolling can end up paying two premiums and still owing a Part B surcharge for the months they were eligible and unenrolled.

The exception is narrow: if Medicare was already in place before COBRA began, the two can coordinate. Anyone approaching 65 is better served by enrolling rather than leaning on COBRA.

The same 20-employee test applies to your spouse’s employer. Where that plan is primary, Part B can wait. Where it is not, enroll at 65 and let the group plan act as secondary coverage.

There is also a younger-spouse angle. Some households keep employer coverage specifically to insure a partner under 65 until Medicare age arrives. That can justify a delay on its own, provided the plan is creditable.