In procurement, the internal requisition for materials or services triggers a procurement process. Purchase requisitions are internal documents that are used to ask your purchasing department to procure a particular quantity of a material or service for a particular date.

A purchase requisition can be created directly or indirectly.
"Direct" means that a purchase requisition is created manually in the department that has the need. Whoever creates the purchase requisition determines which material or service in which quantity, and for which date, has to be ordered.
"Indirectly" means that the purchase requisition from another component is created automatically. Purchase requisitions can be created automatically in the following ways:
In material requirements planning (MRP.)
With maintenance orders
With production orders
With networks
When you manually create a purchase requisition for a material with a material master record, the system supports you during data entry by copying data from the material master record to the purchase requisition. You also have the option of selecting items from a web-based catalog.
You can convert purchase requisitions into RFQs, purchase orders, or outline agreements.
Specifics in Purchase Requisitions
Special Features for Converting Purchase Requisitions

Purchase requisition items with the account assignment category Unknown:
In contrast to the purchase requisition, the account assignment category Unknown (U) is only allowed in the purchase order in connection with the Service and Limit item types. In all other situations, you must select a valid account assignment object and maintain the corresponding account assignment details when creating the purchase order.
Purchase Requisition Items with Material Master Record:
If an info record exists for the supplier and the material, the system proposes the purchase price from the info record when you create a purchase order with reference to a purchase requisition (without source of supply). If no info record exists, you must enter the price manually. The valuation price from the purchase requisition item is not transferred to the purchase order.
Purchase Requisition Items Without Material Master Record:
If the system transfers a purchase requisition item to the purchase order without a material master and without a source of supply, the system proposes the valuation price from the purchase requisition as the purchase price. The buyer can change this default price.