Many of us get frustrated by the fact that once an item is delivered, it cannot be returned.  This is especially difficult if a Supplier miss quotes a part you have raised a PO for, sends it out and then once you have marked it as delivered, it has to be returned, only to be replaced on your original PO by a different item.  Unfortunately as delivered items cannot be returned, you cannot then amend and resend an accurate PO.  I found a temporary work around by taking a back up, duplicating the PO, deleting the old one before saving the duplicate, changing the next PO number in Settings, deleting the now incorrect line, saving the PO (now with the old number) and adding a new line.  Doing this meant I was able to email the now correct Order before restoring to by original backup.  It is not ideal but a way around this problem.  Obviously the PO now sitting on my system is incorrect, but at least the supplier has a correct one! Not a manageable idea if a few of you are working on the system, but it worked for me.  Ideally there needs to be a return feature for delivered items, so please seriously consider this.