Question: Who is the Medicare Secondary Payer? Is that Tricare? Codify Subscriber Answer: The term “Medicare Secondary Payer” refers to situations where another payer has primary payment responsibility for care provided to a Medicare beneficiary. Medicare Secondary Payer (MSP) is different from a “Medicare supplement insured” patient (also known as Medigap), in which Medicare is always primary and there is a secondary private health insurance policy. Several factors determine whether Medicare is primary or secondary, such as the patient’s age or employment status, as well as diagnoses such as end stage renal disease. For instance, if the patient has Medicare as well as group coverage through a large employer, the private (employer-backed) payer would usually be primary and Medicare would be secondary. So determining which payer is secondary or primary comes down to who the other payer is. If the patient has Medicare and Tricare, you should submit the claim to Medicare first, and then the balance bill can go to Tricare.