Invoice best practice means two different things depending on whether you are issuing or receiving, and both come down to the same underlying idea: making the document easy for the other side to act on. A supplier who invoices well is paid sooner; a buyer who processes well pays accurately and stops receiving chasing calls.
If you are sending
Quote the buyer's purchase order reference, prominently. Bill the address they asked you to use rather than an individual you happen to know. Use a unique number, state your terms, and itemise in the units the order used. Those four are what make an invoice clear an automatic match rather than land on somebody's desk for investigation.
If you are receiving
One monitored arrival address with the date recorded. Validation before matching. Exceptions carrying their reason and routed to whoever can resolve them. And an explicit closure for every invoice rather than letting the open list fill with items nobody is pursuing, which is how a queue stops being trusted.
What both sides gain from a reference
The purchase order number is the single field that decides whether an invoice can be checked automatically or has to be investigated by a person. Buyers should insist on it and say what happens if it is missing; suppliers should quote it because a referenced invoice is paid materially sooner in most organisations.
And what both sides gain from a remittance
A note listing which invoices a payment covered lets the supplier allocate it without telephoning. Buyers who send remittances receive fewer queries; suppliers who receive them produce statements that reconcile. It costs nothing and it is one of the few improvements with no trade-off at all.
Questions people ask about invoice best practices
What makes an invoice hard to process?
No purchase order reference, the wrong legal entity, units of measure that differ from the order, and arriving at an individual rather than a monitored address.
Should invoices without a reference be returned?
Many organisations do. Decide it as a policy, tell suppliers in advance, and apply it consistently, or it produces friction without changing behaviour.
Does invoicing promptly help?
Yes, on both sides. Late invoicing distorts accruals for the buyer and delays cash for the supplier, and it is entirely within the supplier's control.