Final answer:
A bidding trail is needed to show that the purchasing staff engaged in bidding, show that an employee found the best price before completing a purchase requisition, and ensure that purchase orders were fulfilled by suppliers.
Step-by-step explanation:
A bidding trail is needed to show that the purchasing staff engaged in bidding, and to show that an employee found the best price before completing a purchase requisition. It is also needed to ensure that purchase orders were fulfilled by suppliers.