Final answer:
The purchasing document given to the supplier by the buyer is called a Purchase order. It specifies what the buyer wants to purchase, and once accepted by the supplier, it becomes a binding agreement. The invoice is a separate document for requesting payment.
Step-by-step explanation:
The name given to the purchasing document completed by the buyer and given to the supplier is D. Purchase order. This document details the types, quantities, and agreed prices for products or services. The supplier uses the purchase order to fulfill the order. It becomes a binding contract once the supplier accepts it. An invoice is subsequently issued by the supplier to the buyer to request payment for the goods or services provided.