An invoice has two jobs. It has to give your customer everything they need to pay you, and it has to satisfy whoever audits either of you later. Most of what people add beyond that is decoration.
The fields that get you paid
Who you are. Your trading name, address and a way to reach you. If a query goes unanswered the invoice goes to the bottom of the pile.
Who they are. The legal entity you are billing, not the person who briefed you. Getting this wrong is one of the most common reasons an invoice sits unpaid in an accounts inbox.
A unique invoice number. Their system will file against it and refer to it in every reply. See numbering your documents.
The date, and the date payment is due. “Net 30” alone is ambiguous. Give the actual date and the argument disappears.
What they are paying for. One line per thing, described the way the customer would describe it. “Consultancy” invites a question; “Discovery workshop, 14 August” does not.
The amount, and how to pay it. Bank details, or a payment link. If you take mobile money, say which number and which name it is registered to.
The fields the auditor wants
These vary by country, so check yours, but the usual list is:
- Your tax registration number, where you have one.
- The customer’s tax number, on business to business sales in many places.
- The tax rate and the tax amount shown separately from the net.
- The words that make it a tax invoice, if your jurisdiction requires a specific form of words.
If you are not registered for tax, do not put a tax line on the invoice at all. An invoice that shows tax you are not entitled to charge is a problem worth avoiding.
A purchase order number, if they gave you one
In any business large enough to have a purchasing process, an invoice without the PO number will be rejected without being read. Ask for it before you start the work, not after you have sent the bill.
What does not help
A long payment terms clause in six point type does not make people pay faster. Neither does a logo three times the size of the total. The things that shorten payment are a correct entity name, a correct PO number, an unambiguous due date, and being easy to pay.
The one thing people forget
Say what happens next. A single line, “Payable by 12 September to the account below”, does more than a paragraph of terms. It tells the reader what you want, by when, and how.