When does the PO status shows as 'Pre- Approved'?
Pre–Approved document is one in which a person with the final authority to approve the purchasing document approves it, but then forwards it to someone else for additional approval, thus changing its status to Pre–Approved.
Your organization uses encumbrance budgeting (reserves funds for documents), and the purchasing document is eligible for approval but funds have not yet been reserved for it. Even if someone with sufficient approval authority approves this document, its status may still remain Pre–Approved if funds were not able to be reserved at the time of approval. Once funds have been reserved for the approved document, the document changes its status to Approved.
A Pre–Approved document does not show up as supply for planning module until its status changes to Approved.