Creating a purchase order is five steps, three of which are checks rather than typing. Done properly it takes a minute and prevents an exception weeks later; done carelessly it takes the same minute and produces an invoice somebody has to investigate. The difference is entirely in the checks.
Get a number and state the lines
A unique number issued automatically, never reused. Then each line with a description the supplier will recognise, the quantity, the unit of measure and the unit price. Vague descriptions and mismatched units are the two things that turn an ordinary invoice into an exception, and both are fixed at this moment or not at all.
Check the entity and the price basis
Is this the supplier's correct legal entity, the one that will actually invoice you. And does the unit price include delivery, packaging and tax or not. Both are quick to confirm and both cause recurring mismatches when assumed. If the supplier is new, these are worth establishing at setup rather than per order.
Approve, send, record
Approval before the order leaves, by whoever has authority for that value. Then send it, and record that it was sent and when. That last step answers whether the supplier ever received it, which is the first question in a good share of delivery disputes and is otherwise reconstructed from somebody's sent items.
Questions people ask about how to create a po
Does the supplier need to acknowledge it?
Useful rather than essential. It removes a class of dispute and matters much less than tracking what actually arrives.
What if the order changes?
Record a dated revision rather than overwriting, and send the revision to the supplier so both sides hold the same version.
Should terms be on every order?
Yes. Terms on the order are what you rely on when the supplier's invoice states different ones.