How to Write an Invoice: A Step-by-Step Guide
Key points
- An invoice needs seven things: your details, the client's details, a unique number, dates, itemised charges, the total due, and payment terms.
- Write a specific due date, not just "Net 30". Ambiguity is what delays payment.
- Payment details belong on the invoice itself. An invoice a client cannot pay from is an invoice that waits.
- Late payment is normal, not personal: 59% of US small businesses are carrying overdue invoices, according to QuickBooks' 2026 report.
What does an invoice have to contain?
An invoice must identify who is billing, who is being billed, what is being charged for, how much is owed, and when payment is due. Everything else is optional. A missing invoice number or due date is the most common reason a finance team returns an invoice unpaid.
The full field list, and what each field is actually for, is covered in what to include on an invoice.
How do you write an invoice, step by step?
Work top to bottom in the order below. Each step answers a question the person paying will ask, in the order they will ask it.
1. Add your business details
Your trading name, address and contact email. If you are a sole trader, your own name is fine. Include a tax registration number if you have one, because the client's accountant will need it to reclaim tax.
2. Add the client's details
The legal entity being billed, not the individual you deal with. Invoices addressed to a person rather than the company are a routine cause of rejection at larger clients. Ask for the billing address and any purchase order number before you send.
3. Give it a unique invoice number
Sequential is easiest: 001, 002, 003. Never reuse a number and never skip backwards. This number is how both sides refer to the invoice afterwards, so it does more work than it looks like it does.
4. Add the issue date and the due date
Write both as real dates. "Net 30" alone forces the reader to do arithmetic, and an invoice that has to be interpreted gets set aside. Write "Issued 6 August 2026, due 5 September 2026" and the deadline is unarguable.
5. List what you are charging for
One line per item or block of work, each with a description, a quantity and a rate. Descriptions should mean something to someone who was not in the room: "Homepage design, 3 rounds" rather than "Design work".
6. Show subtotal, tax and total
Show the arithmetic rather than only the final figure. Subtotal, then any discount, then tax, then the total due. Tax is normally calculated on the subtotal after the discount, and shipping is added afterwards. The total due should be the largest number on the page.
7. State how and when to pay
Bank details, payment link, or both. Add your payment terms and any late fee. This is the step most often skipped, and skipping it guarantees a delay while the client emails to ask how to pay you.
What does a finished invoice look like?
A worked example for a freelancer billing a single project, using the structure above.
| Section | Example content |
|---|---|
| From | Meridian Studio, 12 Broad Street, Lagos, hello@meridian.studio |
| Bill to | Wayne Enterprises Ltd, 1007 Mountain Drive, accounts@wayne.com |
| Invoice number | INV-014 |
| Dates | Issued 6 August 2026 · Due 5 September 2026 |
| Line items | Brand identity system, 1 × $4,800 · Art direction, 6 days × $950 |
| Totals | Subtotal $10,500 · Tax 7.5% $787.50 · Total due $11,287.50 |
| Payment terms | Net 30. Bank transfer to Access Bank 0123456789. 1.5% monthly on overdue balances. |
A minimal but complete invoice. Every line here exists because someone paying it needs it.
What are the mistakes that delay payment?
Most late payments are caused by the invoice, not the client. These five account for the majority of avoidable delay.
- No purchase order number. Many companies will not process an invoice without one. Ask for it before you send, not after.
- Addressed to a person, not the company. Finance teams need the legal entity.
- No payment details. Every day spent asking how to pay you is a day added to the wait.
- Vague line items. "Consulting" invites a question. Questions add weeks.
- A due date expressed only as a term. Write the date.
How long do invoices actually take to get paid?
Longer than the terms say. Xero's US Small Business Insights put the average wait for a small-business invoice at 28.8 days in 2026. QuickBooks' 2026 Small Business Late Payments Report found 59% of US small businesses were carrying overdue invoices, up from 47% the year before, with an average of $17,700 outstanding.
Two practical conclusions. Assume payment arrives after the due date and plan cash accordingly. And make the invoice itself as easy to pay as possible, because the parts you control are the number, the dates, the detail and the payment instructions.
Frequently asked questions
Do I need to be a registered business to send an invoice?
No. A sole trader or freelancer can invoice under their own name. You need a way to be identified and paid, which means your name, contact details and bank or payment details. Registration matters for tax, not for whether an invoice is valid.
What should the first invoice number be?
Start at 001 or 0001 and increase by one each time. The only rule that matters is that numbers are unique and never reused, because the number is how both sides reference the invoice in a dispute or an audit.
Can I send an invoice before finishing the work?
Yes, and for larger projects you should. A deposit invoice for part of the fee up front is normal practice. If the work is not yet agreed, send a quote or a proforma invoice instead, which sets out the cost without demanding payment.
Should I charge a late fee?
State one on the invoice even if you rarely enforce it. A clause such as "1.5% per month on overdue balances" gives you a stated position to point at when chasing payment, and it changes how the invoice is prioritised by a finance team.
Put this into practice. The invoice generator is free, needs no signup, and produces a PDF with real selectable text in 104 currencies.
Create an invoice