How to Write an Invoice (With a Worked Example)

Writing an invoice isn't hard. Writing one that gets paid on the first try, without a "can you resend this with our PO number?" email three weeks later, takes a little more care. This guide goes through it in the order you'd actually fill one in, then shows a finished example.

The short version

An invoice needs to say who is billing whom, for what, how much, by when, and how to pay. In practice that means:

1. The word Invoice at the top
2. A unique invoice number
3. The invoice date
4. Your details: business name, address, email, and tax number if you have one
5. Your client's details: name, and address for business clients
6. Line items: what you did or supplied, with quantity and price
7. Subtotal, tax and total
8. Payment terms and the due date
9. How to pay you
10. Any reference the client gave you, like a purchase order number

Everything else is optional. If you want the full rules, including what the UK and EU legally require, see what to include on an invoice.

Step 1: Put "Invoice" and a number at the top

It sounds obvious, but a document titled "Bill" or with no title at all can get stuck in a client's inbox because nobody's sure what it is. Use the word Invoice. If you're registered for VAT or GST in some countries, you may need "Tax invoice" instead.

The number has to be unique, and it's best if it's sequential. INV-0001, INV-0002 and so on is perfectly fine. Some people prefer a year prefix (2026-014) or a client code (ACME-003). What matters is that you never reuse one. Our guide to invoice numbering covers the formats that hold up best.

Step 2: Date it, and decide when it's due

The invoice date is the day you issue it. The due date is when payment is expected. You can write the due date directly or express it as terms:

• Due on receipt: pay now
• Net 14: 14 days from the invoice date
• Net 30: 30 days from the invoice date

Writing the actual date ("Due 15 September 2026") gets you paid faster than writing only "Net 30", because nobody has to count. Do both if you like. The trade-offs between different terms are in our payment terms guide.

Step 3: Add your details and your client's

Your side: business name (or your own name if you're a sole trader), address, email, phone. If you're registered for VAT, GST or sales tax, add the registration number. That's a legal requirement in many places, not decoration.

Their side: the client's legal business name and billing address. If you're dealing with a larger company, ask who invoices should go to. Many firms route everything to an accounts payable inbox, and an invoice sent to your friendly contact in marketing can sit in their inbox while they're on holiday.

Step 4: Describe the work clearly

This is where most invoices go wrong. "Consulting: $3,000" is technically an invoice, but it invites questions. Compare:

Vague	Clear
Design work	Homepage redesign: 3 layout concepts + 2 revision rounds
Repairs	Replace kitchen mixer tap (parts $84, labor 1.5 h)
Services, August	Bookkeeping, August 2026: 42 transactions reconciled, VAT return prepared

Each line should let someone who wasn't in the room understand what they're paying for. If you bill by time, list hours and your hourly rate; see how to invoice for hours worked.

Step 5: Do the math (and show it)

Show the subtotal, then any discount, then tax, then the total. If the client already paid a deposit, show that too and the balance due. Hiding the arithmetic makes an invoice harder to approve, not easier.

On tax: only charge it if you're registered to collect it. If you are, show the rate and the amount separately. In the UK and EU, a VAT invoice has to show the VAT at each rate. In the US, sales tax depends on the state and on whether what you sell is taxable at all.

Step 6: Tell them exactly how to pay

An invoice with no payment details is a request for another email. Give the client everything they need:

• Bank transfer: account name, bank, account number and routing/sort code (or IBAN and SWIFT for international clients)
• A payment link, if you use a card processor
• The reference to use, usually the invoice number

A worked example

Here's a finished invoice for a freelance web designer, Maya Ortiz, billing a small bakery.

Invoice INV-0047 Invoice date: 1 August 2026, Due: 31 August 2026 (Net 30)

From: Maya Ortiz Design, 12 Clover Lane, Portland, OR 97214, maya@mayaortiz.design Bill to: Crumb & Co. Bakery LLC, 480 SE Division St, Portland, OR 97202 PO: CC-2026-18

Description	Qty	Rate	Amount
Website redesign: 5 pages, mobile layouts	1	$2,800.00	$2,800.00
Online ordering page setup	1	$650.00	$650.00
Product photography editing	24	$12.00	$288.00
Subtotal			$3,738.00
Less deposit paid 10 July			−$1,000.00
Balance due			$2,738.00

Payment: Bank transfer to Maya Ortiz Design, [bank details], reference INV-0047. Late payments may incur a 1.5% monthly fee.

Why this works: the number and dates are at the top, the client's PO is included (their accounts team will look for it), each line explains itself, the deposit is visible, and there's no question about how to pay. Oregon has no sales tax, so there's no tax line. In other states, whether a service is taxable varies a lot, so check with your state's revenue department.

Mistakes that slow payment down

• Sending it late. Invoice the day the work is done or delivered. An invoice sent three weeks later tells the client you're not in a hurry.
• Wrong recipient. Ask up front who approves and pays invoices.
• Missing PO number. For many companies, no PO means no payment. Full stop.
• Rounding surprises. If you quoted $2,800 and invoice $2,950, explain the difference on the invoice.
• PDF named "invoice.pdf". Name it with the number and client, like Invoice-INV-0047-Crumb-Co.pdf. It's easier for both of you to find later.

There's a longer list in common invoicing mistakes.

After you send it

Put the due date in your calendar. If it passes without payment, send a polite reminder the next day. Most late invoices are forgotten, not disputed. Our payment reminder templates give you wording for the first, second and final nudge.