What is proof of delivery and why does it matter for invoice disputes?

Proof of delivery takes different forms by business type. A product shipper has a signed delivery confirmation or tracking scan. A service business might have a signed completion certificate, a client approval email, a project sign-off document, or a timestamped access log showing the customer used the deliverable. A software developer or designer often has the email thread where the client confirmed receipt of final files. Any contemporaneous record that the customer received and acknowledged the work counts.

Where this matters in practice is in disputes. When a customer claims they never received an invoice, never received the work, or that the work was never completed, proof of delivery is the document that resolves the claim. Without it, you're in a tough spot. Even if you actually performed the work, proving it in small claims court or to a collections agency without documentation is much harder. A signed completion acknowledgment from the customer closes most disputes quickly.

Best practice for service businesses is a brief "completion and handover" email at the end of every engagement listing what was delivered and asking the client to reply confirming receipt. Most clients reply without friction, and the reply creates a timestamped, written proof of delivery that costs nothing to produce. For larger projects, a formal sign-off document signed by both parties is worth the extra step.