How to Write an Invoice

Writing an invoice sounds simple until you’re staring at a blank page wondering what actually needs to be on it. Here’s the complete list, and why each piece matters.

The essentials

• A unique invoice number — makes tracking and referencing the invoice possible for both sides.
• Your business details — name, address, and contact info, so the client knows who’s billing them.
• Client details — name and billing address, matched to how they’ll process the payment internally.
• Invoice date and due date — the due date should reflect your actual payment terms (Net 30, due on receipt, etc.).
• Itemized line items — description, quantity, unit price for each item or service.
• Tax, if applicable — the rate and amount, calculated clearly.
• Total amount due — the final figure, impossible to miss.
• Accepted payment methods — how you want to be paid.

Order matters more than people think

Put your business and the client’s details near the top, followed by the invoice metadata (number, date, due date), then the itemized table, then totals, then any notes or payment instructions last. This mirrors how most people actually read an invoice — top-down, business context first, dollar amount last.

Step-by-step: writing your first invoice

1. Choose a tool or template. A word processor works, but an invoice generator calculates totals and due dates for you, which removes the most common source of errors.
2. Add your header. Put “Invoice” at the top so it can’t be mistaken for a quote or receipt, then your logo, business name, address, email and phone.
3. Add the client’s billing details. Ask who pays invoices — often an accounts-payable team rather than your day-to-day contact — and use the company’s legal name.
4. Assign an invoice number. Use a sequential system that never repeats. Our invoice number generator can help you set one up.
5. Add the invoice date and due date. Pick terms you agreed — due on receipt, Net 15, Net 30 — and write the actual date.
6. List the goods or services. One line per item, with a clear description, quantity, unit price and line total.
7. Calculate the totals. Subtotal, then any discount, then tax, then shipping, then the total due.
8. Explain how to pay. Bank details, a payment link or accepted card types — whatever makes paying easiest.
9. Add notes. A PO number, late-payment terms, and a thank-you.
10. Check, save and send. Proofread names and numbers, save a copy for your records, then email it as a PDF.

A worked example

Say you’re a designer billing a client for a logo and business cards, with 8% sales tax on the printed cards only:

Subtotal $990.00 + tax $7.20 = total due $997.20, due 30 days from the invoice date. Notice the tax applies only to the taxable line — our generator lets you set a different tax rate on each line for exactly this reason.

Writing good line-item descriptions

The description is where most invoices go wrong. Compare:

• Weak: “Design work — $900”
• Strong: “Logo design — 3 initial concepts, 2 rounds of revisions, final files in AI, PNG and SVG — $900”

A strong description answers the questions an accounts-payable clerk would otherwise email you about: what was delivered, how much of it, and over what period. For hourly work, include the dates or the period (“Development, 1–15 May, 22.5 hrs”).

Invoice requirements outside the US

In the US there’s no single federal invoice format, but tax rules shape what you include. Elsewhere, requirements are often stricter. In the UK and EU, a VAT invoice must generally show your VAT number, the date of supply, the VAT rate and amount for each rate, and the customer’s details; in Australia, a tax invoice must include your ABN and the words “Tax invoice” when GST applies. If you’re registered for a consumption tax, check your tax authority’s list of required fields.

Common mistakes to avoid

• Forgetting the due date — “Net 30” alone can be misread; write the date too.
• Reusing or skipping invoice numbers.
• Sending it to the wrong person or department.
• Omitting a purchase order number the client requires.
• Math errors in totals or tax.

We cover these in more depth in Common Invoice Mistakes That Delay Payment.

After you send the invoice

• Record it in your tracker or accounting software with its number, amount and due date.
• Confirm receipt for large invoices — a quick “Just checking this reached you” saves weeks later.
• Follow up on the due date if it’s unpaid; see our follow-up guide.
• Send a receipt once paid, if the client wants one.
• Keep copies for your tax records.

Frequently asked questions

What is the correct format for an invoice?

A typical invoice has a header with the word ‘Invoice’ and your business details, the client’s details, an invoice number, the invoice and due dates, an itemized table of goods or services, a totals section with tax, and payment instructions.

Can I write an invoice in Word or Excel?

Yes. You can also fill in our generator and download a ready-made Word or Excel file with the totals already calculated.

Do I need a registered business to write an invoice?

No. In most countries individuals and sole traders can invoice under their own name.