Account Assignment for Direct Procurement Purchase Requisitions 
Use
Purchase requisitions, which are created by the system during direct procurement, bypass the warehouse and are set with the account assignment category Unknown. (The account assignment category U is set in Customizing as a default value in the SAP Standard System.)
In make-to-order planning and individual project planning too, the system sets the purchase requisitions for direct procurement with the account assignment category Unknown. The system does not pass on the account assignment for the sales order or the project to the purchase requisition for direct procurement.
Features
If the planned order that caused a purchase requisition for direct procurement is converted into a production order, then the purchase requisition is automatically reassigned to the production order account. If the purchase order does not have to be created until the production order exists, then the purchase order is also automatically assigned to the production order account.
If, due to deadlines, you have to order before the production order exists, then you have to manually assign the purchase order to a service cost center account. Here, you must select an item category that allows account assignment to cost center and that leaves the goods receipt non-valuated.
If the production order still does not exist when the invoice is received, the costs remain with the service cost center. Otherwise, you must manually change the account assignment from the service cost center to the production order when posting the invoice receipt.
Activities
You see the number of the respective production order, if you display the account assignment of the purchase requisition for direct procurement. To do this, proceed as follows:
The item overview of the purchase requisition now appears.
The account assignment screen for the item appears. In the Order field, you will find the number of the superior production order.