How to Write a Professional Invoice
A professional invoice needs your business details, a unique invoice number, itemized charges, payment terms and a due date. Here's what every invoice should include and how to structure it.
What every invoice needs
A complete invoice has: your business name and contact details, the client's name and contact details, a unique invoice number (for your own records and theirs), the invoice date and a payment due date, an itemized list of products or services with quantity, rate and line total, a subtotal, any tax, and the final total due.
Invoice numbering that doesn't cause problems later
Use a consistent, sequential numbering scheme from day one — even something simple like INV-0001, INV-0002 — rather than dates or client initials alone. It sounds minor, but a broken or duplicate numbering scheme is one of the most common bookkeeping headaches small businesses run into once they're a year or two in and have an accountant asking questions.
Setting clear payment terms
State the due date explicitly ("Due: March 15, 2026") rather than just "Net 30" — plenty of clients don't do the math and pay late as a result. If you charge late fees or offer early-payment discounts, state the exact terms on the invoice itself, not just in a separate contract, so there's no dispute about what was agreed.
Create this document now
Frequently asked questions
Do I need to charge sales tax on an invoice?
It depends on what you're selling and where — many services aren't taxable at all in most US states, while physical goods usually are. Check your state's specific rules, since this varies a lot and getting it wrong is a common small-business mistake.
What's the difference between an invoice and a receipt?
An invoice is a request for payment, sent before or at the time of a sale. A receipt confirms payment was already received. They serve opposite ends of the same transaction.
Is there a different invoice format for freelancers?
The core fields are the same, but freelancers often bill by the hour or by project milestone rather than fixed line items — see our freelance invoicing guide for that structure specifically.