Doing a purchase order properly is not more work than doing one carelessly; it is the same work with three checks added. The checks take seconds and they prevent the exceptions that consume hours in payables weeks later, which makes order raising one of the highest-leverage minutes in the whole purchasing cycle.
Before you type
Confirm you are ordering from the supplier's correct legal entity, that the units of measure match how they will invoice, and that you know whether the quoted price includes delivery and tax. New supplier, new conversation. Existing supplier, these should already be on their record so nobody has to ask twice.
While you type
A unique number issued automatically. Lines with descriptions the supplier will recognise, quantities, units and prices. A delivery address and a date, because that date is what makes the open-order report actionable. And your payment terms, which are what you rely on if their invoice states something different.
Before it leaves
Approval by whoever has authority for the value, then send it and record that it was sent and when. Approval before issue is the control; approval afterwards is a review of a commitment that already exists. Recording the send answers whether the supplier ever received it, which is the first question in most delivery disputes.
Questions people ask about how to do a purchase order
How long should this take?
A minute for a familiar supplier. The checks are only slow the first time you deal with somebody.
What if it needs changing later?
Record a dated revision, send it, and re-approve if the value increase passes your threshold.
Who should raise orders?
Whoever buys, within a role that has a value limit. Concentrating it in one person is a bottleneck; letting anybody do it is not a control.