What Is an Invoice? Meaning, Examples and What to Include

Billsato · Updated 9 October 2026 · 8 min read

An invoice is a document a seller sends to a buyer to ask for payment for goods or services. It lists what was sold, what each item costs, the total owed, and when and how to pay. For both sides it is also the written record of the sale.

That is the short answer. The rest of this guide covers what an invoice has to include, what the law asks for in different countries, the main types of invoice, how an invoice differs from a receipt, a bill or a quote, and how to make one.

Invoice meaning in one minute

• Who sends it: the seller (a business, a freelancer, a contractor).
• Who receives it: the buyer, often called the client or customer.
• When: after the work is done or the goods are delivered, or at agreed stages of a longer job.
• What it does: asks for payment, records the sale, and backs up both sides' tax records.
• What it is not: proof of payment. That is a receipt.

The word itself is old. English borrowed it in the 1500s from the French envois, "things sent", the plural of envoi (a dispatch of goods). An invoice was the list that travelled with a shipment, and that is still roughly what it is today.

What an invoice does

An invoice looks like a simple bill, but it does four separate jobs:

1. It asks to be paid. It states the amount, the due date and how the customer can pay.
2. It records the sale. Your income and your customer's expense are both based on it, so both of you keep a copy.
3. It supports tax filings. Tax authorities use invoices to check sales tax, VAT or GST, and in many countries a business can only reclaim VAT if it holds a valid invoice.
4. It sets the terms. Payment terms, late fees and what exactly was delivered are written down, which helps if there is ever a dispute.

What to include on an invoice

Requirements vary by country (more on that below), but a complete, professional invoice includes these details:

1. The word "Invoice" at the top, so nobody mistakes it for a quote. Where you are registered for VAT or GST, many countries expect "Tax invoice" or "VAT invoice".
2. A unique invoice number. Numbers should run in sequence, for example INV-0001, INV-0002, with no gaps or repeats.
3. The invoice date (the date you issue it) and, if different, the date the goods or services were supplied.
4. Your details: business or trading name, address, email or phone, and any tax registration number such as a VAT, GST or ABN number.
5. Your customer's details: name or company name and address. For business customers in the EU, their VAT number is often required too.
6. A description of what you supplied: each product or service on its own line, with quantity, unit price and line total.
7. Subtotal, tax and total: the amount before tax, the tax rate and amount, any discount, and the final amount due.
8. The due date and payment terms, such as "Due on receipt" or "Net 30" (payment within 30 days).
9. How to pay: bank details, a payment link or the payment apps you accept.
10. Notes where useful: a purchase order number, a project name, late payment terms or a thank-you.

A simple invoice example

Here is what the core of a small service invoice looks like:

Above the table sit the seller's and customer's details, the invoice number (say INV-0042), the invoice date and the payment terms. Below it go the payment instructions.

Do invoices have legal requirements?

Yes, in most countries, once you are registered for a sales tax such as VAT or GST. Here is how it works in a few large markets. Always check your own country's tax authority, because rules change.

European Union

The EU VAT Directive (Article 226) lists what a VAT invoice must contain. It includes the date of issue, a sequential number that uniquely identifies the invoice, the seller's VAT number, the customer's VAT number in some cases, both parties' full names and addresses, the quantity and nature of what was supplied, the date of supply, the taxable amount per rate, the VAT rate and the VAT amount. Each member state writes these rules into its own law, sometimes with extras.

United Kingdom

VAT-registered UK businesses must issue VAT invoices that show their VAT registration number, the time of supply, the price per item excluding VAT, the VAT rate, and the totals with and without VAT. For sales of £250 or less including VAT you can issue a simplified invoice with fewer details.

Australia

A GST-registered business must give a tax invoice when a customer asks for one, within 28 days, unless the sale is $82.50 or less including GST. The invoice must show that it is a tax invoice, the seller's identity and ABN, the date, a description of what was sold with quantity and price, the GST amount, and how much of the sale is taxable. From $1,000 it must also show the buyer's identity or ABN.

United States

There is no single federal invoice format. What matters is that your invoices are accurate, kept with your records and show any sales tax correctly. Sales tax is set by each state, and in many states services are not taxed at all.

Countries where a PDF is not enough

A growing number of countries require e-invoicing: structured invoices sent through a government system or an approved network rather than a PDF by email. Italy has required it for business sales since 2019, Mexico (CFDI), Brazil (NF-e), Turkey (e-Fatura), Saudi Arabia (ZATCA) and India (for larger businesses) have their own systems, Belgium made it mandatory for business-to-business sales in January 2026, France starts phasing it in from September 2026, Poland from 2026 and Germany from 2027. The EU plans e-invoicing for cross-border business sales from July 2030. If you trade in one of these places, use the official system for tax invoices. A PDF invoice is still useful for quotes, proforma invoices and customers abroad.

Types of invoices

• Standard invoice: the everyday request for payment after a sale.
• Proforma invoice: a preliminary invoice sent before the sale, showing what the buyer will be charged. It is often used for customs or to arrange payment in advance, and is not a demand for payment.
• Interim or progress invoice: bills part of a long project as stages are completed. Common in construction (see our contractor invoice guide).
• Final invoice: closes a project and accounts for earlier progress payments and deposits.
• Recurring invoice: the same charge on a schedule, such as a monthly retainer or maintenance contract.
• Timesheet invoice: bills hours worked at an hourly rate. Typical for freelancers and consultants (see our freelance invoice guide).
• Credit note: reduces or cancels an invoice already sent, for a return, an overcharge or a mistake.
• Debit note: increases the amount owed on an earlier invoice, for example for extra charges.
• Commercial invoice: used in international trade. Customs use it to value goods and work out duties, so it includes details such as country of origin and tariff codes.

Invoice vs receipt, bill, quote and purchase order

The simplest way to remember it: a quote comes before the work, an invoice asks for money, and a receipt confirms the money arrived.

How to create an invoice

1. Add your business details and logo, if you have one.
2. Add your customer's details, and their purchase order number if they gave you one.
3. Give the invoice a number and a date, continuing your sequence.
4. List each item or service with quantity and price.
5. Add tax, discounts and shipping where they apply.
6. Set the due date and payment terms, and add how to pay.
7. Check it and save it as a PDF, then send it and keep a copy.

You can do all of this in Billsato's free invoice generator: fill in the form, watch the PDF update as you type, and download it. There is no sign-up and no watermark, and what you type stays in your browser.

When to send an invoice, and how

Send it as soon as the work is delivered. The longer you wait, the longer you wait to be paid. For long projects, agree on stage payments or a deposit before you start. Email with a PDF attached is the fastest and most common way to send an invoice. Put the invoice number, amount and due date in the email itself, not only in the attachment.

Late payment is common: in a 2025 Atradius survey of US companies, 43% of the value of business-to-business invoices was overdue. If a due date passes, our guide to payment reminder emails has a schedule and templates you can copy.

How long to keep invoices

Keep a copy of every invoice you send and receive. How long depends on your country. The US IRS generally asks for three years from filing, and up to seven years in some situations. HMRC in the UK asks sole traders to keep records for at least five years after the 31 January filing deadline, and limited companies for six years. Many other countries set five to ten years.

Sources

• Etymonline: invoice
• Council Directive 2006/112/EC, Article 226
• GOV.UK: Invoices, what they must include
• Australian Taxation Office: Tax invoices
• IRS: How long should I keep records?
• Global Trade Review: Atradius Payment Practices Barometer 2025 (Americas)
• vatcalc: EU ViDA e-invoicing timeline