I totally understood decreasing purchqty, If the order has been already received or invoiced.
B.U.T.
Even though the partially or fully received/invoiced, Should the purchqty be possible to increase?
When I try to increase puchqty, I got a error with as below.
“You are attempting to enter values that will change the source document amounts for this purchase order. Because invoicing of this purchase order has started, you are not allowed to make changes to these values.”
You cannot increase quantity in case the PO is partially/fully invoiced. If the PO is partially invoiced, you can add a new line for the same item for additional quantity. If it is fully invoiced, generate a new PO & add the additional quantity on new PO.
If you are trying to add a quantity to receive in because you have another delivery you are willing to accept you can change the deliver remainder and add another to allow delivery. However if the order is invoiced and you want to order another 1 I would suggest a new purchase order, if you need to keep the same PO number a new line.