Which of the following is NOT considered a standard source of supply in SAP S/4HANA?

In SAP S/4HANA, standard sources of supply typically include established methods for creating procurement documents and identifying vendors who can provide required goods or services. Among the options provided, a purchase order, vendor list, and contract are all recognized as standard sources of supply.

The purchase order represents a formal commitment to a supplier to purchase specific goods or services, and it's a crucial document in the procurement process. The vendor list contains information about approved suppliers from whom an organization can procure goods or services. Contracts also serve as legal agreements that establish terms and conditions for procurement activities, providing a framework for purchasing over time.

On the other hand, while a purchase requisition is important in the procurement process for initiating a purchase request, it is not classified as a source of supply. Instead, a purchase requisition identifies the needs of an organization and acts as a request to procure items, but it does not directly represent a supplier or a legally binding agreement. Hence, the correct answer regarding what is NOT considered a standard source of supply in SAP S/4HANA is the purchase requisition.