How to write an invoice that gets paid on time (with a checklist)

An invoice gets paid on time when the client can approve it without asking you a single question: it names the right person, shows exactly what was done, states the amount and the due date, and says how to pay. Most late payments start with a missing detail, not with a bad client.

This guide covers what the invoice must contain, how to word the payment terms, when and how to send it, and a checklist to run through before you send.

What must an invoice contain?

Every invoice needs the same core fields:

• The word "Invoice" at the top, so nobody mistakes it for a quote.
• A unique invoice number. Use a simple running sequence such as 2026-014. Never reuse a number.
• Issue date and due date. Write the due date as a real date, not only "30 days".
• Your details: name or company, address, email and any registration or tax number your country requires.
• The client's details: the exact company name and the person or department that pays invoices.
• Line items: what you delivered, the quantity or hours, the unit price and the line total.
• Totals: subtotal, tax if you charge it, and the total due, with the currency written out.
• Payment instructions: bank details or payment link, and the reference the client should use.

Which tax lines and registration numbers are required differs by country. Confirm the rules with your local tax authority or an accountant before you copy a layout from the internet.

How should you word the payment terms?

Vague terms get vague payment. Compare:

Payment due soon.

Payment due by 14 November 2026 (14 days from issue). Pay by bank transfer to the account below and quote invoice 2026-014.

The second version leaves nothing to interpret. Three habits help:

1. Agree the terms before the work starts, in the quote or contract, and repeat them on the invoice.
2. Pick short terms you can defend. 7, 14 or 30 days are common. Shorter is not rude; it is clear.
3. State your late-payment policy only if your contract supports it. Whether you may charge late fees or interest depends on your agreement and local law, so check before you add a percentage.

For larger projects, split the invoice: for example 50% before you start and 50% on delivery. You carry less risk and the final invoice is smaller and easier to approve.

When should you send it?

Send the invoice on the day the work is accepted or delivered. Every day you wait pushes the payment date back by a day, because the client's clock starts when they receive the invoice, not when you finish.

If the client's accounts team pays in a monthly run, ask for the cut-off date once and send your invoice before it. An invoice that arrives one day after the cut-off can wait a whole extra month.

How should you send it?

• Send a PDF, not a screenshot or an editable file. It looks the same on every device and is easy to file.
• Put the invoice number in the email subject: "Invoice 2026-014 – Website copy – due 14 Nov".
• Send it to the person who pays, and copy your contact. If you do not know who that is, ask.
• Keep the email to three lines: what it is, the amount and due date, how to ask a question.
• Attach purchase-order numbers if the client uses them. Many companies reject invoices without one.

What about reminders?

Plan them before you send the invoice, so chasing is routine and not personal:

1. A short reminder two or three days before the due date.
2. A note on the due date if nothing has arrived.
3. A firmer message a week after, restating the amount, the date and the payment link.

Log each reminder in your records so you can see which invoices are open at a glance.

12-point checklist before you press send

1. The invoice says "Invoice" and has a unique number.
2. Issue date and due date are real dates.
3. Your legal name and contact details are correct.
4. The client's name matches their contract.
5. The right person or department receives it.
6. Each line says what was delivered, not just "services".
7. Quantities, prices and totals add up.
8. Tax lines follow your local rules (confirmed, not guessed).
9. The currency is written next to the total.
10. Bank details or payment link are correct. Test the link.
11. The PO number or project reference is included, if the client uses one.
12. The file is a PDF named clearly, for example invoice-2026-014-northwind.pdf.

Keep track after you send

An invoice is only half the job. You also need to know which ones are sent, due soon, paid or overdue, and how much money is still outside your account. A simple register with a due-date column and a status formula does it. If you would rather not build one, the Small Business Invoice & Client Manager includes an invoice register with automatic Paid, Due or Overdue status and a printable A4 invoice.