Did you know that in Microsoft Dynamics GP 2013 we added functionality to the Purchase Order Closing process?  Now you can prevent a purchase order from closing if it has an unmatched quantity.

 

You will be warned if you try to close a purchase order when the quantity invoices doesn't match the quantity shipped.

 

In Edit Purchase Orders each line on the Purchase Order will check the quantity shipped and quantity invoiced.  If they don't match you will get a warning when you try to close the line.  If you try to close the purchase order it will check all lines and give a warning.

You will be able to proceed and close anyway if you want.