Feature lists for purchase order management software are long and largely interchangeable. Two capabilities are worth insisting on regardless of size or price, because they are cheap to have in any product and effectively impossible to add later, and because everything useful downstream depends on them.
Quantities per line, three of them
Ordered, received and invoiced, held against each line rather than each document. Ordered minus received is your chase list. Received minus invoiced is your accrual. Invoiced above received is what the three-way match is for. A product tracking only document totals cannot answer any of the three.
Revisions kept with their dates
Prices change and quantities are amended. A system that overwrites looks tidier and destroys the record of what was agreed when, which is precisely what a supplier disagreement turns on. Dated revisions cost nothing at the time and are the difference between a ten-minute conversation and a week of searching email.
And an export you can read
Orders, lines, receipts, revisions and approvals, in a format you can open without the vendor. Organisations change purchase order systems more often than they expect, usually because they outgrow the first one, and an export missing receipt history makes that move considerably more painful.
Questions people ask about software for purchase order management
How do we test quantities per line?
Order ten, receive four, invoice four, and ask what is outstanding. The answer should be six on that line.
Does our accounting package do this?
Many create orders; fewer track partial receipts at line level. Check that specifically rather than the presence of a purchase order feature.
What if the product is otherwise perfect?
Then it is a document generator with a good interface, which is a legitimate purchase if you know that is what you are buying.