To write an invoice, list who is billing whom, what you delivered, what it costs, and when and how to pay. Give it a unique number and a due date, and send it the day the work is done.
That's the short version. Below are the details every invoice needs, an example you can copy, and the small mistakes that quietly push payment back by weeks.
What to include on an invoice
- Your business details. Your business name (or your own name if you work for yourself), address, email, and logo.
- Your client's details. Their company name, the contact responsible for paying, and their billing address.
- An invoice number. Unique and sequential, like INV-0042. It's how everyone refers to the invoice later.
- The invoice date. The day you issue it. Payment terms usually count from this date.
- A due date or payment terms. A specific date, like "Due April 30", or terms like Net 30. See invoice payment terms explained.
- Line items. A clear description of each service or product, with the quantity or hours, the rate, and the amount.
- Subtotal, discounts, taxes, and total. Show any tax as its own line, at the rate that applies.
- How to pay. The payment methods you accept, ideally with a link to pay online by card or bank transfer.
- Tax and reference numbers, when required. Your tax or VAT number where your country requires it, and the client's purchase order (PO) number if they gave you one.
- A short note. A thank-you, and your late fee policy if you have one.
Invoice example
Here's how those pieces come together for a small design project:
Acme Design Co. · 123 Market St, San Jose, CA · [email protected]
Bill to: Greenleaf Botanicals, Attn: Dana Lee, 45 Oak Ave, Portland, OR
Invoice: INV-0042 · Date: April 1, 2026 · Due: May 1, 2026 (Net 30) · PO: GL-1187
| Description | Qty | Rate | Amount |
|---|---|---|---|
| Brand strategy workshop | 1 | $2,400.00 | $2,400.00 |
| Logo design, 3 concepts and revisions | 1 | $4,800.00 | $4,800.00 |
| Design hours, packaging adaptations | 12 | $125.00 | $1,500.00 |
| Subtotal | $8,700.00 | ||
| Total due | $8,700.00 | ||
How to pay: Pay online by card or ACH at the link in this email. Thank you for your business! A 1.5% monthly late fee applies to balances unpaid after the due date.
How to write an invoice, step by step
- Start from a template or an invoicing tool. It keeps your layout consistent and numbers your invoices for you. See our free invoice templates.
- Fill in both parties' details. Double-check who on the client side approves payment.
- Itemize the work. Write descriptions the person paying will recognize, not internal shorthand.
- Set the terms. Choose a due date, and state any deposit already paid or late fee policy.
- Send it promptly. Email a link with a pay button, attach a PDF if needed, and copy anyone who approves invoices.
- Follow up. If the due date passes, send a polite reminder. Our payment reminder email templates can help.
Common invoicing mistakes that delay payment
- No due date. "Upon receipt" is easy to ignore. A specific date is not.
- Vague line items. "Services, $5,000" invites questions, and questions pause payment.
- Sending to the wrong person. Your day-to-day contact often isn't the one who pays.
- Missing the PO number. Many larger companies can't pay an invoice without one.
- Making payment hard. If paying means typing in bank details, many clients will put it off.
- Waiting to invoice. The longer you wait after delivering, the longer you wait to be paid.
How Clientary helps
Clientary numbers your invoices automatically, puts your logo and brand on every one, adds a pay button for card and bank payments, and sends reminders when invoices go overdue. You can also turn tracked time and expenses into invoice lines in a few clicks.
