How to Write an Invoice
An invoice is a formal request for payment that records what you sold, to whom, and how much they owe. Getting it right matters for two reasons: it's how you get paid on time, and it's a legal and accounting document both you and your client rely on at tax time.
This guide walks through each part of an invoice in order, so you can write one from scratch — or fill one out in a couple of minutes with a generator and know exactly what every field is for.
1. Label it as an invoice and give it a number
Put the word "Invoice" clearly at the top so there's no confusion with a quote or a receipt. Then assign a unique invoice number. Numbers should be sequential and gap-free — INV-001, INV-002, and so on — because in many countries you're required to be able to account for every number in the series.
Pick a scheme and stick to it. Sequential numbers, per-client prefixes (ACME-001), or year-based numbers (2026-014) all work, as long as no number repeats and none is skipped.
2. Add your details and your client's details
Include your business name (or your own name if you're a sole trader), address, and contact email. If you're registered for a sales tax like VAT or GST, add your registration number here too.
Then add who you're billing: the client's name and address. For business-to-business sales, include their tax registration number if your local rules require it.
3. List the work with quantities and rates
Give each product or service its own line: a short description, the quantity (hours, units, or a flat 1 for a fixed fee), and the rate. The line total is quantity times rate, and the sum of the lines is your subtotal.
Be specific in descriptions. "Website design — 12 hours" tells the client more than "Services rendered" and heads off payment questions before they start.
4. Apply discounts and tax
If you're giving a discount, subtract it from the subtotal before tax. Then calculate any sales tax — VAT, GST, or a state sales tax — on the discounted amount, and add it to reach the total. Always show the tax rate and amount as their own line so the client can see how the total was built.
If you're not registered to charge tax, simply leave it off; don't add a tax line you're not entitled to collect.
5. State the total, the due date, and how to pay
Show the amount due prominently, along with the currency. Add the issue date and a clear due date — "Net 14" or "Net 30" (14 or 30 days from the issue date) are common terms.
Finally, tell the client how to pay: bank details, a payment link, or whatever methods you accept. The easier you make payment, the faster you get paid.