A purchase order is a short document and every field on it has a job, usually one that becomes apparent weeks later when an invoice arrives. Reading one field by field, with what each is for, explains why payables cares so much about a document that purchasing regards as routine, and it explains which fields cause trouble when they are vague.
Identity and reference
Your organisation's details and the supplier's, a unique order number, and the date. The number is the handle everything hangs on: the supplier quotes it, the delivery note carries it and the invoice references it. Getting the supplier's legal entity right matters too, because an invoice from a different entity of the same group will not match cleanly.
The lines, which are what gets matched
Each line carries an item description, a quantity, a unit of measure and a unit price. These are compared against the invoice, so vagueness here becomes an exception later. Units of measure are a classic source of trouble: ordering by box and being invoiced by unit produces a quantity mismatch that is nobody's error and takes a person to resolve.
Delivery and terms
Where and by when, and your payment terms. Terms on the order are what you rely on if the supplier's invoice states different ones, which happens often enough to matter. Including them costs a line and prevents a category of disagreement that is otherwise resolved by whoever argues longest.
Questions people ask about purchase order example
Does a purchase order have to be a formal document?
It has to be clear and unique. Formality helps mainly because a consistent layout means suppliers find your reference where they expect it.
Should we include a delivery date?
Yes. It is what makes an open-order report actionable, since without it you cannot tell which deliveries are late.
What if the price is not known?
State an estimate and mark it as such, or use a not-to-exceed value. An order with no price gives the match nothing to compare against.