What has to be on an invoice

An invoice has one job: to be paid without anyone needing to ask you a question. Most of what belongs on it follows from that.

Always

• The word Invoice, so it is not mistaken for a quote
• A unique invoice number
• The date of issue, and the date payment is due
• Your business name, address and contact details
• The client’s name and address
• What you supplied, itemised, with quantity, unit and unit price
• The total, and the balance due if a deposit has been paid
• How to pay, and the reference to use

If you are tax registered

• Your tax identification and registration numbers
• The taxable amount before tax
• Each tax or levy on its own line, with its rate
• The client’s tax number, where the rules require it

Do not fold several taxes into one percentage. A client reclaiming tax needs to see the components separately, and an auditor will ask why they cannot.

Not required, but they stop questions

• A purchase order number. In larger organisations an invoice without one can sit unpaid indefinitely. Ask for it before you invoice.
• The name of the person who commissioned the work. Accounts payable needs to know who approves it.
• Dates or a period the work covers. Turns a vague line into something checkable.
• Units. “12” means little; “12 hours” means something.

Write descriptions the client can approve

The person paying is often not the person you worked with. “Consultancy” forces them to go and ask. “Consultancy, June, brand workshop and handover” can be approved on sight. Specific descriptions are paid faster.

One number should dominate

Whoever opens the document should find the amount due without reading anything else. Everything above it is evidence for that number.