How to Write an Invoice: A Step-by-Step Guide

Why a clear invoice matters

An invoice is more than a request for money. It is a record for both you and your client, supports your tax filings and — when it is clear — gets paid faster. Most payment delays come from missing information: a missing PO number, an unclear due date or no instructions on how to pay.

The essential elements of an invoice

Include each of the following on every invoice:

• The word “Invoice” and a unique, sequential invoice number
• Invoice date and payment due date (or payment terms such as Net 30)
• Your business name, address and contact details
• Your client's name, company and billing address
• An itemized list of products or services with quantities, rates and line totals
• Subtotal, discounts, each tax charged and the total amount due
• Your sales tax, GST/HST or VAT registration number, if registered
• Payment instructions and accepted payment methods

Step by step

1. Start with your branding: add your logo and business details so the invoice is immediately recognizable.

2. Add your client's details exactly as they appear in their accounts system — and their purchase order number if they gave you one.

3. Number the invoice. Use a consistent sequence such as INV-0001, INV-0002 so every invoice can be traced.

4. Itemize the work. Short, specific descriptions (“Website design — 6 pages”) prevent questions.

5. Apply taxes and discounts. Charge tax on the discounted price unless your local rules say otherwise.

6. State terms and how to pay. Give a due date, payment methods and any late-fee policy.

7. Review and send as a PDF so the formatting cannot change.

Common invoicing mistakes

• Reusing or skipping invoice numbers
• Vague line items that the client has to ask about
• Forgetting the due date — “whenever” is not a payment term
• Charging the wrong tax rate for the client's location
• Sending an editable document instead of a PDF