How to write an invoice, step by step

What an invoice is and when to send one

An invoice is a dated, numbered request for payment that lists what you supplied, what it costs and when the money is due. Send it when the work is delivered, at an agreed milestone, or on the schedule in your contract. Sending it the same day you finish keeps the job fresh in the customer’s mind.

An invoice is not proof that anyone has paid. That job belongs to a receipt, which you issue after the money arrives. If you are unsure which document a customer is asking for, our guide to the difference between an invoice and a receipt sets them side by side.

Timing matters for three reasons. Your payment clock usually starts on the invoice date, so a late invoice means late money. Some tax offices set a deadline for issuing tax invoices once a sale happens. And a customer who receives a bill months after the work is more likely to question it.

What to gather before you start writing

Collect six pieces of information before you open a template: your legal or trading name and contact details, your tax number if you have one, the customer’s billing name and address, any purchase order number they gave you, the dates and quantities of the work, and the payment terms you agreed. Having these ready turns a twenty minute job into five.

• Your details: business name, address, email, phone, and your GST, VAT or other tax number if you are registered.
• The customer’s details: the exact company name their accounts team uses, a billing address, and the person or inbox that approves invoices.
• Their reference: a purchase order (PO) number, project code or job number. Large customers often reject invoices that lack one.
• The work: dates, hours, units and the agreed price for each item. Pull these from your timesheet, quote or delivery notes.
• The terms: how many days the customer has to pay, any deposit already received, and any discount you agreed.
• Payment details: bank account, card link or other method you accept.

The full list of fields that belong on the page, and which ones are legally required in different places, is in our guide on what to include on an invoice.

How to write an invoice in 8 steps

Work from the top of the page down. Start with a layout, add both parties, number and date it, list the line items, apply any discount and tax, total it, and finish with the due date and payment instructions. Each step below takes a minute or two once your details are saved in a template or tool.

1. Choose a layout. Use a template or a generator rather than a blank page, so the math and alignment are handled for you. Our free invoice generator runs in your browser and saves your business details for next time.
2. Add your business details. Put your name, address and contact details at the top. Add your tax number if you are registered for GST, VAT or sales tax.
3. Add the customer. Write their billing name and address, plus the contact who will approve payment and any PO number.
4. Number and date the invoice. Give it the next number in your series and today’s date. Add the date of supply if it differs from the issue date.
5. List each item. One line per product or service, with a short description, quantity, unit price and line total. Be specific: “Bathroom regrout, 6 m², 14 October” beats “Labor”.
6. Apply discounts and tax. Subtract any agreed discount, then add tax at the correct rate if you are registered. If you are not registered, charge no tax.
7. Total it. Show the subtotal, discount, tax and final amount due. Subtract any deposit already paid so the balance is clear.
8. State when and how to pay. Give a real due date, not only “net 14”, and list your payment details. Then save it as a PDF and send it.

If you bill similar work often, a ready made layout such as the small business invoice template saves you rebuilding the same structure each time.

Worked example: a service invoice from start to finish

Here is a complete invoice from a made up design studio, Harbor Line Studio, to a made up client, Pinecrest Family Dental. It has three line items, a 5% returning client discount, tax at an example rate of 10%, and 14 day terms. Every figure is worked to the cent so you can check the math yourself.

Invoice number INV-2026-0118, dated 3 November 2026, PO number PFD-7731. Prices are examples only.

The terms line reads: “Payment due within 14 days, by 17 November 2026. Bank transfer to the account below, quoting INV-2026-0118.” Writing both the term and the actual date removes any argument about when the clock started.

Notice the order. The discount comes off before tax, so tax is charged on the price the customer actually pays. If your tax office has a specific rule about discounts, follow it.

Adding GST, VAT or sales tax to the invoice

Add tax only if you are registered for it or required to collect it. If you are registered, show your tax number, the rate on each line or for the invoice, the tax amount and the total including tax. If you are not registered, leave tax off entirely and do not call the document a tax invoice.

That last point is a legal rule in some places. In Australia, business.gov.au states that a business not registered for GST must not use the words “tax invoice” on its regular invoices. In the UK, a VAT invoice must show your VAT registration number and the total VAT in sterling, according to HMRC’s VAT Notice 700.

Rates and rules change by country and sometimes by product, so check the official guidance for where you trade. These guides walk through the math for each system:

• Adding GST to an invoice (Australia, New Zealand, India, Singapore, Canada)
• Adding VAT to an invoice (UK, Ireland, South Africa, UAE)
• Sales tax on US invoices

If a customer has asked specifically for a tax invoice, read what makes a document a tax invoice first, since the required details can be stricter than for an ordinary bill.

Sending the invoice and keeping a copy

Send the invoice as a PDF so the layout cannot shift and the numbers cannot be edited by accident. Email it to the person or inbox that approves payments, put the invoice number in the subject line, and keep your own copy in a folder named by year. A short covering note with the amount and due date helps it get approved.

A clear file name makes the invoice easy to find on both sides. A pattern like INV-2026-0118 Harbor Line Studio.pdf sorts neatly and tells the reader what it is before they open it. For wording you can paste into the email, see our invoice email templates.

Keep every invoice you issue, including ones you later cancel. Your numbering should show no unexplained gaps, and your tax records will rely on these copies. Our guide to invoice numbering covers how to handle a voided number.

If you want to send invoices from a dashboard and see when each one is paid, WhizInvoice, our sister app, does that on its free plan. For a one off invoice, a PDF and an email are all you need.

A 60 second check before you press send

Read the invoice once as if you were the customer’s accounts clerk. Check that the name matches their records, the PO number is there, every line adds up, tax is right or absent, the due date is a real date, and your bank details are correct. A single small error is enough to send an invoice back and hold up payment.

• Customer name and billing address match what they gave you.
• Invoice number is new and follows your series.
• Each line total equals quantity times unit price.
• Discount and tax are applied in the right order.
• Due date is written as a date, for example 17 November 2026.
• Bank details are complete and you have checked them against a statement.

For a longer list of errors and how to avoid them, see common invoice mistakes.