Purchase order vs invoice

A purchase order usually comes first and authorizes spend. An invoice comes when payment is requested for delivered or agreed work or goods.

The buyer creates the PO. The seller creates the invoice. Confusing the two documents is common in casual conversation but costly in accounting.

Matching PO → delivery/acceptance → invoice is how larger companies control spending. Help them by aligning descriptions and totals.

PO purpose: internal permission and vendor instruction. Invoice purpose: request payment and create a receivable.

The PO protects the buyer from unauthorized purchases. The invoice protects you by formally stating what is owed and when.

Neither replaces a clear scope of work. You still need agreement on what “done” means.

Mirror PO line descriptions on the invoice when possible. If the PO says “Q3 creative retainer – July,” do not invoice “Design stuff.”

Match totals and currency. Even small variances can kick an invoice into manual review for weeks.

Include PO number, invoice number, and billing entity name exactly as the client expects—legal entity mismatches are a silent killer of timely payment.

You quote $6,000 for a campaign. Client issues PO-7781 for $6,000. You deliver. You send INV-9120 for $6,000 referencing PO-7781. AP three-way matches and pays Net 30.

If you later add $800 of approved extras, get a PO amendment or additional PO before invoicing the extra—or expect a delay.

What to do next: for every enterprise invoice this month, verify the PO number appears on the PDF before you hit send.

Many small clients never issue POs. In that case your accepted quote plus invoice is the commercial trail.

If a client sometimes uses POs and sometimes does not, ask which rule applies to this job. Assumptions create unpaid limbo.

Remember: absence of a PO does not mean absence of terms—put payment terms on the invoice anyway.