How to Write an Invoice

Most late payments are not disputes. They are invoices that were unclear, went to the wrong person, or arrived without the one detail the client's finance team needed. Getting those right is most of the work. The invoice layouts here put every required field in a fixed place; the wording and the terms are still yours to set.

What has to be on it

1. Your business name and contact details - the same ones on your letterhead, so a client filing both sees one business rather than two.
2. The client's name, and where it matters, the department or person who approves payment.
3. A unique invoice number.
4. The issue date and, separately, the due date.
5. A line for each thing you are charging for, with an amount.
6. The total, set larger than everything around it.
7. How to pay - bank details, or a note saying they are available on request.

Number them in sequence

INV-2026-001, INV-2026-002, and so on, with no gaps. Gaps are the first thing an auditor asks about, and a client querying an invoice will always quote the number rather than describe the work.

Put a date, not a term

"Net 14" means nothing to somebody outside finance. "Due 22 September 2026" is a date a person can act on. Where you use both, the date is the one that gets read.

Send it to the right person

The person who hired you is often not the person who pays you. Ask, at the point of agreeing the work, who invoices should go to and whether they need a purchase order number on them. An invoice missing a PO number sits in a queue until somebody asks about it.

Chasing without damage

A short, factual reminder on the day after the due date, referencing the invoice number and re-attaching the invoice, resolves most late payments. It works because the usual cause is an invoice sitting unapproved, not an unwillingness to pay. Escalate to the person who hired you only after the second reminder.

Keep a copy of everything

Save every invoice as a PDF the day you send it, named with its number. Whatever your tax authority requires, the practical reason is simpler: when a client asks which invoice covers which month, you want to answer in one minute rather than one afternoon.