When you become eligible for ESRD Medicare, your employer group health plan will pay first and Medicare will pay second. This is called the 30-month coordination period. The 30-month coordination period begins when you are first eligible for Medicare based on ESRD, even if you haven’t signed up for it yet. For example, if Mr. X begins dialysis at a facility in September of 2011, he is eligible for Medicare in December, 2011. Mr. X does not enroll in Medicare until June, 2012. His 30-month coordination period still began in December, 2011.
The 30-month coordination period applies to both insurance based on current and former employment. This means that current employer insurance, retiree insurance and COBRA all pay first and Medicare pays second. After the 30-month coordination period, Medicare pays primary to your employer coverage. This means that Medicare will pay first for all Medicare-covered services and your employer group health plan will pay second.
If you do not have any insurance but Medicare, Medicare pays primary on all claims as soon as you enroll.