How to write an invoice that gets paid: the 9 fields that matter

An invoice is a request for money that someone else's bookkeeper has to process. Every missing field is a reason for it to sit in a queue. Here is what to include on an invoice, and why each item is there.

Late payment is rarely about a client refusing to pay. Far more often the invoice arrived without a number, or without the client's own reference, or with a total that did not match the quote, and it stalled in someone's inbox. The fix is boring: put the right nine things on the page, every time. Below is what each one is, what goes wrong when it is missing, and a checklist you can run before you send.

The 9 fields

1. The word "Invoice" and a unique invoice number

Label the document clearly so nobody mistakes it for a quote or a statement. Then give it a number that you never reuse. Sequential is simplest (INV-0042, INV-0043). The number is how the client's accounts team files it, how you chase it, and how you match the payment when it lands. UK guidance lists a unique identification number as the first thing an invoice must include (GOV.UK: Invoicing and taking payment from customers), and the same expectation applies almost everywhere.

2. Your business details

Your name or trading name, address, email and phone. If you are registered for VAT or sales tax, add the registration number. If you trade as a limited company, use the registered company name. The point is that the person paying can identify exactly who they owe, and their auditor can too.

3. The client's details

Their business name, address and, if you have it, the name of the person who commissioned the work. Larger clients often require a purchase order number on the invoice before they will pay at all; if they gave you one, put it near the top.

4. Invoice date and supply date

Two different dates. The invoice date is when you issued the document; the supply date is when you delivered the goods or finished the service. They are often the same day for a freelancer, but not always, and payment terms usually count from the invoice date, so record both.

5. Line items: description, quantity, unit price, line total

One row per thing you are charging for. Be specific enough that someone who was not in the room understands it: "Homepage redesign, 12 hours at $90" beats "Design work". Vague descriptions invite questions, and questions delay payment. If the work was fixed-price, quantity 1 and the agreed fee is fine.

6. Subtotal, tax, discount and total due

Show the arithmetic. Subtotal of the line items, any discount (state whether it is an amount or a percentage), tax at a stated rate, then the total. Put the total in the largest type on the page. If your invoice has a total that does not visibly follow from the lines above it, expect an email.

7. Due date and payment terms

Write an actual date, not just "Net 30". "Due 4 October 2026" is unambiguous; "Net 30" makes the client's bookkeeper do arithmetic, and they will not do it in your favour. State the terms alongside it so the date has context. If you have not agreed a payment date with a business customer in the UK, the default under GOV.UK guidance is that they must pay within 30 days of receiving the invoice or the goods or service (same source). Shorter terms are normal for small jobs; just make sure the client agreed to them before the work started.

8. How to pay you

Bank name, account name, account number and sort code or routing number; IBAN and BIC for international clients; or the payment link if you take cards. The number of invoices delayed because "we didn't have your bank details" is embarrassing. Put them on every invoice, even for repeat clients.

9. Notes and late-payment terms

A short thank-you is fine. More useful is a line about what happens if payment is late. In the UK, business-to-business invoices carry a statutory right to charge interest on late payment at 8% plus the Bank of England base rate, plus a fixed recovery cost (GOV.UK: Late commercial payments). Other countries have their own rules, and you do not need to invoke any of them; simply stating that late payments incur interest tends to move your invoice up the pile.

The checklist

Run this before every send. It takes thirty seconds.

• Says "Invoice" and has a number I have not used before
• My name, address, contact details and tax number (if registered)
• Client's name and address, plus their PO number if they gave one
• Invoice date and supply date
• Each line item has a clear description, quantity, unit price and line total
• Subtotal, discount, tax rate and total are shown and add up
• A specific due date, with the payment terms next to it
• Bank details or payment link
• Late-payment terms (and, optionally, a thank-you)
• Total matches the estimate or quote the client accepted
• Saved a copy of the PDF in my records

Estimates vs invoices: do not mix them up

An invoice asks for payment for work that is done or agreed. An estimate proposes a price for work that has not started. They look similar, which is exactly why the label matters: a client who receives a document titled "Invoice" before any work has happened will, reasonably, assume you are billing them for nothing.

Keep them on separate number sequences (EST-0007 and INV-0042, not two documents both called 0007), send the estimate first, and when the client accepts, create the invoice from it so the line items and total match. If the final invoice needs to differ from the estimate, say why in the notes field. The full breakdown, including where quotes fit in, is in Invoice vs estimate vs quote: when to send which.

Three mistakes that cost the most time

1. Sending it to the wrong person. The person who hired you is often not the person who pays. Ask for the accounts-payable address up front and copy your contact.
2. A total that does not match the quote. Even a legitimate change in scope needs a sentence of explanation, or it becomes a dispute.
3. No copy kept. If you make invoices in a browser tool that stores nothing on a server, the PDF you download is the only record. The IRS suggests keeping records that support your income for generally three years (IRS: How long should I keep records?). A dated folder of PDFs is enough.