Do you have old Purchase Orders hanging out there in various statuses that are complete as far as you are concerned but just won’t go away?  Here are suggestions on clearing them out:

If the ‘Ordered’ quantity is more than the quantities ‘Received’ and ‘Invoiced’ , simply edit the ‘Ordered’ to equal the same amount as those ‘Received’ and ‘Invoiced’.  The next time purchases are posted, this Purchase Order will be removed.

If the ‘Received’ quantity is higher than the ‘Ordered’ quantity, this purchase order needs to be completed by applying the invoice to the ‘Received’ goods.  Then you can create a Debit Memo to remove those items from Inventory.

Purchase Orders will be removed once all line items have been received and invoiced.  So the main clue to cleaning up old Purchase Orders is to make sure each line of the Purchase Order has been satisfied.