Guide
Numbering purchase orders so accounts can actually match them
Duplicate and re-used PO numbers are the most common cause of an invoice sitting unpaid in a query pile.
Unique, and never reused
One number, one order, forever. Reusing a number because an order was cancelled is what makes an invoice impossible to match, and an invoice that cannot be matched does not get paid until somebody has a phone call about it.
Sequential beats descriptive
The temptation is to encode meaning: supplier initials, job codes, dates. It reads well for a month and then two orders collide on the same day, or a job gets renamed. A plain sequential run with the meaning held in the fields, not the number, survives contact with a busy year.
Prefix if you have separate streams
Where genuinely separate streams exist, a short prefix on its own sequence is worth it: PO-1001 for general, SUB-1001 for subcontract. Two streams is usually the sensible limit.
Cancel, don't delete
If an order dies, mark the number cancelled and leave the gap closed. A missing number in a sequence is the thing an auditor asks about, and 'we deleted it' is a worse answer than a cancelled record.
Put the number on everything after it
Delivery note, packing list, invoice, credit note. The PO number is the thread that ties a pile of paper into one transaction, and its whole value is that it appears on all of it.
Do it now
Raise a numbered purchase order, and turn it into a delivery note when the goods go out. Free, no signup, and the numbering carries through.
Open the free purchase order template