How to write an invoice: what to include and how to number it

Published 2 October 2026 · Freelancing and getting paid

An invoice is a request for payment for goods or services you have delivered. A clear, complete invoice gets paid faster, because the client's accounts team can approve it without coming back to you with questions.

What to include on an invoice

1. The word "Invoice" at the top, so it is not mistaken for a quote or a statement.
2. Your details: business name, address, email and phone, and your tax registration number if you are registered for VAT, GST or sales tax.
3. The client's details: the legal name of the business you are billing and its address, plus a contact or department if they asked for one.
4. A unique invoice number (see below).
5. The invoice date, and the date you delivered the goods or finished the work if it is different.
6. The client's purchase order number, if they gave you one. Many larger companies will not pay an invoice without it.
7. Line items: what you supplied, the quantity or hours, the rate and the amount for each line.
8. Subtotal, discounts and tax, each shown separately, and the total due.
9. Payment terms and the due date, such as "Net 30, due 15 November 2026".
10. How to pay: bank transfer details, a payment link or where to send a check.
11. Late payment terms, if your contract allows a late fee or interest.

How to number invoices

Give every invoice its own number in a sequence you never reuse, such as 2026-001, 2026-002 and so on. A year prefix keeps numbers short, and some businesses add a client code (ACME-014). Do not reuse or skip numbers without a reason: gaps invite questions from an accountant or a tax inspector, and some tax systems require sequential numbering; EU VAT rules, for example, require a sequential number that identifies each invoice.

If an invoice you have sent is wrong, do not quietly edit it. Issue a credit note that cancels it, or part of it, and a new invoice with a new number, so every document in your records still matches what the client received.

Payment terms and due dates

Agree the payment terms in your contract before you start, and repeat them on every invoice. Common terms:

• Due on receipt: payable as soon as the client gets the invoice.
• Net 7, net 14, net 30: payable within that many days of the invoice date.
• EOM: payable at the end of the month the invoice is dated in, or a set number of days after it.
• 2/10 net 30: a 2% discount if paid within 10 days, otherwise the full amount within 30.

Always print the actual due date as well as the terms, so nobody has to work it out. The invoice due date calculator does it for any of these terms, including early payment discounts.

Sales tax, VAT and GST

If you are registered for VAT, GST or sales tax, the tax authority decides what a valid tax invoice must show, usually your registration number, the tax rate and the amount of tax, and sometimes the client's details too. Check the rules where you are registered. In the US, sales tax is set by each state, and whether a service is taxable differs from state to state. If you are not registered, do not add tax to your invoices.

Late fees and interest

Only charge a late fee or interest your contract allows, and say on the invoice what it is. In the UK, a business invoicing another business can claim statutory interest on late payment at 8% above the Bank of England base rate, plus fixed compensation of £40 to £100 per invoice, even if the contract says nothing. The late payment interest calculator works it out.

Sending the invoice

• Send it as soon as the work is delivered or the agreed milestone is reached. The payment clock starts when the client receives it.
• Send a PDF, so it cannot be changed by accident, to the person or accounts address the client named. Put the invoice number and amount in the email subject.
• Keep a copy of every invoice you send, and note when it was paid.
• If the due date passes, send a polite payment reminder. If that does not work, see what to do when a client won't pay.

Invoices, quotes and receipts

A quote comes before the work and offers a price; an invoice comes after and asks for payment; a receipt confirms you were paid. The guide to the difference between a quote, an estimate and an invoice explains when to use each one.

Free templates

The free invoice template asks for each item above, including line items, a discount, tax, any amount already paid and your bank details, and builds the invoice in your browser without an account. When the client pays, send a payment receipt. Pricing a new job first? Start with the quote template, and for repeat work a retainer agreement sets the monthly fee and payment terms once.

General information, not tax or legal advice. Invoicing and tax rules differ between countries and states; check the rules that apply to your business.

More on freelancing and getting paid

• How to write a freelance contract: 10 clauses that prevent disputes
• What to include in a statement of work (SOW)
• Quote vs estimate vs invoice: what is the difference?
• What is a kill fee? How to set one in a freelance contract
• What to do when a client won't pay: a step-by-step plan
• How to write a demand letter for unpaid invoices
• What is a change order? How to handle scope changes
• What is a credit note? When to issue one, what it must say

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