How Does Medicare Work With Employer Coverage?

If you have health insurance through an employer when you become eligible for Medicare, the two can work together through rules called coordination of benefits, which decide who pays first. If you or your spouse are still working and the employer has 20 or more employees, the employer plan is usually primary and Medicare is secondary.

When the employer has fewer than 20 employees, Medicare typically becomes primary, which often means you should enroll in Part B at 65 to avoid gaps in coverage. Because the rules hinge on employer size and whether the coverage is from current employment, it is important to confirm how your specific plan coordinates.

If you keep qualifying employer coverage past 65, you can usually delay Part B without a late penalty and enroll later through an eight-month Special Enrollment Period after the coverage ends. Note that retiree coverage and COBRA do not count as current employer coverage for delaying Part B. A licensed Medicare advisor can review your benefits and help you time your enrollment correctly.

It is also worth checking whether your employer plan provides creditable prescription drug coverage, which matters for avoiding a Part D late penalty down the road. Comparing the cost and benefits of your workplace plan against Medicare can reveal which option, or combination, gives you the best value. Reviewing these details before you retire helps you transition smoothly without gaps or penalties.