SAP ME22N

It changes an existing purchase order, quantities, prices, dates or items, subject to what is allowed given the PO’s processing status.

• PO number (opens the PO for editing).
• Editable item fields (quantity, price, delivery date).
• Header/item conditions and texts.
• Release status (if a strategy applies).

• Changes may re-trigger the release strategy (re-approval).
• Some fields lock once goods receipt/invoice exist.
• Use the change documents to see the PO’s history.

• Field not changeable after GR/IR activity.
• Change resets release, requiring re-approval.
• Quantity below already-received amount rejected.

• Changing the price after a goods receipt. The receipt was valued at the old price, so the difference lands in a variance account and becomes somebody's month end question.
• Deleting an item instead of flagging delivery complete. Deletion removes the line and the reason it existed; the completion indicator closes it and keeps the history.
• Asking who changed this before reading the change documents. The purchase order records every field change with the user and the timestamp.
• Moving a delivery date without telling anybody. MRP replans against it immediately, so an optimistic date quietly becomes a shortage in another plant.
• Editing a PO created from a requisition without going back to it. The requisition still says what the requester asked for, and the two now disagree.