A customer may sometimes create an open or standing purchase order which allows the customer to order quantities of the product(s) from the vendor over a period of time (usually a year) at the specified price. An open PO (purchase order) is often used for services which occur over a period of time.
The typical sections of a purchase order are:
- Date
- The purchase order number
- Names and addresses of both the customer and the supplier/vendor.
- Description of the items being ordered, the cost for each, and the total amount.
The PO number is an important reference for both the customer and the supplier.
Source: www.biztaxlaw.about.com