The short answer: if you or your spouse are actively working and you are covered by that employer’s group health plan, you can usually delay Part B without penalty. When the work or the coverage ends, an eight-month special enrollment window opens.
When delaying is safe
The employer coverage must come from current, active employment. Size matters too: for employers with 20 or more employees, the group plan pays first and Medicare can wait. Under 20 employees, Medicare generally needs to be in place at 65, because it pays first.
When it is not
Retiree coverage and COBRA do not count as active employment coverage. Staying on either past 65 without Part B is the most common and most expensive mistake we see, because the penalty is permanent.
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