After a PO has been approved, you cannot modify its details.
To be able to modify an approved PO you must use a Change Order.
To create a change order
1. Open the purchase order you want to edit. With the purchase order on the screen, click the Change Order button.
2. The Purchase Order screen changes to the Change Order screen and the detail lines are cleared.
3. Add the new purchase order details.
4. Click Save.
5. After you have created a change order:
---- The change order displays a link to the parent purchase order (the original purchase order).
---- The original purchase order displays a link to the change order/s.