How To Change A PO After It Is Accepted
To edit a Purchase Order that has been sent or that has been accepted you must first change the status of the PO to Draft. Locate the PO you wish to edit and once in the PO you will see the 'Status' option with a phrase to the effect of 'Completed' next to it.
There will be a small arrow next to the current state which you need to click to alter the state to 'Draft'.
The system will then ask for a reason for the change, e.g "to correct a mistake", or "change in requirements". Fill this out and you will have an editable PO back in draft state.