When you create a PO referred to a requisition, it can happen that deleted requisition items are also copied.
To prevent this you can set the message 06 050 - "Purchase requisition & item & already deleted" to an error message via
IMG transaction => Material Management => Purchasing => Environment Data => Define Attributes of System Messages=> System Messages
But the checks for the messages can only take place, after adopting all positions, including also the deleted ones.
So, what can we do to avoid copying the deleted requisitions items?.
In the transaction ME21N click the "Selection variant" button at Overview screen on the left -> Choose Purchase Requisition
Select the checkbox 'Open only' on the selection screen for the overview.
In this case, the deleted items will not appear on the overview and therefore they can not be adopted.