How to Write an Invoice

An invoice does two jobs. It tells a customer exactly what they owe, by when and how to pay, and it becomes part of your financial records for bookkeeping and tax. A clear invoice gets paid faster and causes fewer questions; a vague one tends to sit in someone's inbox. The good news is that the format is simple once you know what to include.

General information only, not legal or tax advice. What an invoice must legally show, especially around sales tax or VAT, differs by state and country, so check the rules where you trade.

What every invoice should include

• The word "Invoice" at the top, so nobody mistakes it for a quote or estimate.
• Your business details – trading name, address and contact email; your registered company name if you have one.
• The customer's details – their business name, a contact person and their address.
• A unique invoice number – never reused, so each bill can be traced.
• Invoice date and due date – the day you issue it and the day payment is expected.
• A description of the work or goods – specific enough that someone outside the project understands it.
• Quantities, rates and line totals, followed by a subtotal.
• Taxes, if they apply, shown separately with the rate used.
• The total amount due, clearly marked.
• Payment terms and methods – how many days the client has and how they can pay.

A simple layout to follow

Place this table beneath a header block with your details on one side and the customer's on the other, followed by the invoice number and dates. Below the table, add payment instructions and a short thank-you line.

Numbering that keeps you organised

Choose a numbering scheme and stick with it. Sequential numbers work well, and some businesses add a year or a client code in front so records sort neatly. The key rules are that numbers do not repeat and you do not skip around; gaps can raise questions if your books are ever reviewed. If you cancel an invoice, keep a record of it and issue a credit note rather than deleting it.

Writing payment terms people understand

Terms should leave no room for interpretation. "Payment due within the number of days agreed in our contract, by the date shown above" is clearer than an abbreviation that the client's accounts team may read differently. Spell out:

1. the exact due date,
2. accepted payment methods and the details needed for each,
3. what reference the customer should quote with their payment,
4. any late-payment charges, but only if they were agreed beforehand and are allowed where you operate.

Sending it

Most invoices now go out by email as a PDF, which keeps the layout fixed. Address the email to the person who approves payments, not only to the person you worked with, and put the invoice number and amount in the subject line. Accounting and invoicing software can generate numbered invoices, send reminders and record payments, which saves time once you have more than a handful of clients.

Following up when payment is late

Late payment is common and usually not personal; invoices get lost or wait for sign-off. A polite, structured approach works best:

1. Shortly before the due date, send a friendly reminder with the invoice attached.
2. Soon after the due date, ask whether anything is holding up payment and whether they need further details.
3. If it remains unpaid, call the accounts contact and agree a specific payment date.
4. As a last step, consider the formal routes available in your jurisdiction, ideally after taking advice.

Keep every message factual and courteous; it preserves the relationship and creates a clean record if you ever need it.

When invoices tie up too much cash

Even well-run businesses can find that money owed by customers arrives later than bills of their own. Some firms use invoice factoring or similar finance to smooth this out; our article on using factoring to fund your next step explains how it works and what to weigh up. If you are just setting up, our guide on how to start an LLC covers the structure many small firms invoice from.

Quick checklist before you hit send

• Is the invoice number new and in sequence?
• Are both dates present and correct?
• Does every line describe the work clearly?
• Do the totals add up, including any tax?
• Are payment details accurate and easy to copy?

Five checks, a minute of your time, and a much better chance of being paid on schedule.