4. What is Medicare Secondary Payer? Posted on September 11, 2017 at 12:16 pm.Written by advantage_admin This is the term used to determine when the Medicare health coverage is NOT primarily responsible for paying. This process is known as Coordination of Benefits (COB). The Coordination of Benefits is a written statement establishing which health insurance plan or policy will pay first if there are two health insurance plans or policies covering the same benefits. Post navigation 1. What is Triple-S Advantage?5. What is a Medigap policy?