Medicare can either be primary or secondary to your employer coverage. This usually depends on the size of the employer and whether or not someone is currently working.

Primary insurance pays first for health care claims. Secondary insurance pays after the primary insurance for some or all of what the primary insurance did not cover. Knowing which is primary is important because secondary insurance often refuses to pay anything if the primary insurance has not paid first.

Check out this handy infographic explaining when employer coverage is primary and when Medicare is primary.