How to Write a Professional Invoice: Checklist, Example and Tips

A professional invoice does two jobs: it tells your client exactly what they owe and when, and it gives both of you a record that stands up to an accountant or a tax office. Most late payments trace back to an invoice that was missing something, such as a due date, a purchase-order number or bank details.

The ten things every invoice needs

1. The word "Invoice" at the top, so it is not mistaken for a quote or a receipt.
2. A unique invoice number. Sequential numbers such as INV-2026-014 are easiest to audit. Never reuse a number.
3. Issue date and due date. Write the due date as a date ("Due 14 October 2026"), not only as "Net 30".
4. Your details: legal or trading name, address and email. Add your tax number (VAT, GST/HST, BTW, ABN) if you are registered.
5. Your client's details: the company name and billing address, plus a contact name and any PO number they gave you.
6. Line items with a description, quantity, rate and line total. "Website redesign, 3 templates" is clearer than "Design work".
7. Subtotal, tax and total. Show tax as its own line with the rate, for example "VAT 20%".
8. Payment terms, for example "Payment due within 14 days".
9. How to pay: bank details, IBAN/SWIFT for international clients, or a payment link.
10. A short note such as "Thank you for your business" or a reference to the project.

A worked example

A designer billing a UK client for a logo project might send: INV-2026-031, issued 1 Sept 2026, due 15 Sept 2026. Logo design (3 concepts) 1 × £600; Brand guidelines PDF 1 × £250. Subtotal £850. VAT 20% £170. Total due £1,020. Each line maps to something the client agreed to, so there is nothing to query.

Mistakes that delay payment

• Sending the invoice to a general inbox instead of the person who approves payments.
• Missing the client's PO number. Many larger companies cannot pay without one.
• Vague line items that invite questions.
• Charging tax when you are not registered, or leaving your tax number off when you are.

Habits that get invoices paid on time

The invoice itself is half the job. These five habits cover the rest, and each links to the detail.

1. Invoice on the day you deliver. Every day between finishing and invoicing is added to the time it takes to get paid. Make the invoice part of handing over the work, not a job for the end of the month.
2. Agree the terms before you start. Put the payment terms, any deposit and your late-payment policy in the quote or contract, then repeat them on the invoice. On larger jobs a deposit, for example 30% to 50%, means you are never owed more than you can afford to lose (payment terms explained).
3. Remind on a schedule. A short note a few days before the due date, another on the day, and a firmer one about a week after. Send the same way every time so nothing depends on memory (invoice and reminder emails to copy).
4. Keep one line per invoice. A spreadsheet with the invoice number, client, amount, issue date, due date and paid date is enough. Sort by due date once a week and the slow payers show up long before they become a cash-flow problem.
5. Know your late-payment rights. When a business customer in the UK or Ireland pays late, the law lets you add interest and a fixed compensation sum. Work out both with the late payment interest calculator, and read how to charge a late payment fee for the wording.

You can build an invoice with all of these fields in our free invoice generator. The live preview shows exactly what the PDF will look like before you download it.