Diagnosis
You have attempted to delete or block an item whose invoiced and POquantities differ.
You can only delete or block items in respect of which processing hasbeen completed. This means that the invoiced quantity of the goods mustbe greater than or equal to the PO quantity.

Procedure
If you nevertheless want to delete or block the item, proceed asfollows:
Press F12=Cancel.
Change the PO quantity of the item, so that
IR quantity >= PO quantity.
Select the item and choose the option "Delete" or "Block" again.