What is a purchase order (PO) based payment?

Typically, good or services above a certain monetary threshold as defined in the company 
Procurement Procedures or in the Individual Consultants policy require a requisition and purchase
order be created in system with a chosen supplier to fulfil an order. There are exceptions, for
example, when procurement is below a certain threshold, when payments are considered petty
cash, project cash advances, entitlement related payments or payments to implementing partners
or organizations .