Primary payer
Primary payer means, when used in the context in which Medicare is the secondary payer, any entity that is or was required or responsible to make payment with respect to an item or service (or any portion thereof) under a primary plan. These entities include, but are not limited to, insurers or self-insurers, third party administrators, and all employers that sponsor or contribute to group health plans or large group health plans.
Source
42 CFR § 411.21
Scoping language
In this subpart B and in subparts C through H of this part, unless the context indicates otherwise