How do I write an invoice?
How to write an invoice — what to include and how to get paid faster
Short answer
A professional invoice contains specific fields that both document the transaction and make it easy for the client to pay. Missing or vague information is the most common cause of delayed payment.
**Required fields on every invoice:** 1. **Your business name, address, and contact information** 2. **Invoice number** — a unique sequential identifier (INV-001, INV-002, etc.) 3. **Invoice date** — the date you issued the invoice 4. **Due date** — a specific calendar date (not "Net 30" alone) 5. **Client's name, company, and billing address** 6. **Itemized list** — description of each product/service, quantity, unit price, and line total 7. **Subtotal, any taxes, and total amount due** 8. **Payment instructions** — accepted methods, bank details or payment link 9. **Late fee clause** (optional but recommended): "A fee of 1.5% per month applies to balances unpaid after [date]."
**What makes an invoice get paid faster:** - Use a specific calendar due date instead of just "Net 30" - Include a direct payment link (Stripe, Square, PayPal) — removes the friction of figuring out how to pay - Send it the same day you complete the work, not the end of the month - Use your client's PO number if they have one — missing it causes payment delays in enterprise billing systems
**Invoice numbering formats:** - Sequential: INV-001, INV-002 - Date-based: INV-20260508-001 - Client-based: ACME-2026-001
Any format works as long as it's unique and consistent.