Please clarify whether your FIL was a recipient of Medicare, Medicaid or both. Unless, there's a coincidence with the name, CMS (Center for Medcare/Medicaid Services) administers the Medicare and Medicaid programs. The explanation of benefits a patient receives will be from CMS. It's not a collection agency. Are you sure your husband isn't just confusing the explanation of benefits (EOB) from CMS with a bill from the Pharmacy?

If he was on Medicare & Medicaid, or just Mediaid, there should be no balance. If he was just on Medicare, there may be a balance from the portion he owed, but it would be relatively small. Hope this helps to clarify.

I'm not a lawyer, so I cannot answer your question regarding whether your husband is responsible for payment if there isn't an estate.