Who is authorized to change a PR or PO?

Before a PO is sent and accepted, it can be changed by its creator or approver under your own internal rules — a purchase requisition (PR) is purely internal, so editing it just follows your approval workflow. After the supplier accepts the PO, neither side can change it unilaterally: it's a contract, and modifications require agreement from both parties, usually documented as a revised PO or a change order referencing the original PO number.

Good practice regardless of size: changes above a threshold re-trigger approval (a $500 PO quietly edited to $5,000 is the classic fraud pattern), every revision is versioned so the audit trail shows who changed what and when, and the supplier always confirms the revision — a changed PO the supplier never saw isn't an agreement, it's a surprise.