How to Write an Invoice: Step-by-Step Guide with Example

An invoice is a request for payment. It tells your client what you supplied, what it cost, when the money is due and how to pay it. Get those four things right and most invoices are paid without a single follow-up email. Leave one out and you will usually find out a month later, when the payment has not arrived and the client says they were waiting for a PO number, a tax number or your bank details.

This guide walks through how to write an invoice from scratch: what goes on it, in what order, with a complete worked example you can copy. It applies whether you are a freelancer sending your first invoice, a contractor billing after a job, or a small business that has outgrown handwritten bills.

What is an invoice?

An invoice is a document a seller sends a buyer to request payment for goods or services that have been supplied. It records the transaction for both sides: the seller uses it to track what is owed, and the buyer uses it to approve and make the payment. In most countries an invoice is also a tax record, so the details on it matter for your accounts and, if you are registered, for VAT, GST or sales tax.

An invoice is not the same as a quote or a receipt. A quote or estimate comes before the work and says what it will cost. An invoice comes after and asks to be paid. A receipt comes last and confirms that payment was received.

What an invoice must include

Requirements vary slightly by country, but a complete invoice almost always contains the following. Treat this as the minimum:

1. The word "Invoice" at the top, so it cannot be mistaken for a quote or a statement.
2. A unique invoice number. Sequential numbers are standard and expected by most tax authorities.
3. Your details: business or trading name, address, email or phone, and your tax registration number if you have one.
4. Your client's details: their name or company name and billing address.
5. The invoice date and, ideally, the date the goods or services were supplied.
6. The payment due date or payment terms, such as "Due within 14 days".
7. An itemised list of what you are charging for, with a description, quantity, rate and line total for each item.
8. The subtotal, any discount, tax and the total amount due.
9. How to pay: bank details, a payment link or a QR code.

If you are VAT or GST registered there are extra fields. The full list, including the specific rules for the UK, the EU, the US, India, Australia and Pakistan, is in our guide to what to include on an invoice.

How to write an invoice, step by step

1. Choose how you will create it

You can write an invoice in a word processor or spreadsheet, in accounting software, or with an online invoice generator. A spreadsheet works, but you have to build the layout, formulas and numbering yourself, and it is easy to send a file with a broken total. Accounting software is worth it once you send dozens of invoices a month. For most freelancers and small businesses, a free invoice generator is the quickest option: the layout, totals and tax are handled for you and you download a finished PDF.

2. Add a clear header

Put the word "Invoice", your logo if you have one, and your business name at the top. Your client should be able to tell who it is from and what it is at a glance, including when they are scanning a folder of fifty PDFs at the end of the month.

3. Add your business details

Include the name you trade under, your address, and an email address or phone number the client can use if they have a question. If you are a limited company, use the full registered company name. If you are registered for VAT, GST or sales tax, add your registration number here - in many countries an invoice without it cannot be used by the client to reclaim tax.

4. Add your client's details

Write the name of the person or company you are billing and their billing address. For a business client, check whether they need the invoice addressed to a specific department or person, or need their purchase order (PO) number on it. Large companies often cannot pay an invoice that is missing a PO number, and they will not always tell you.

5. Give it a number and dates

Assign the next number in your sequence - 0001, 0002 and so on, or a format such as 2026-014. Never reuse a number, and do not skip numbers without a reason. See how to number invoices for formats that work.

Then add the invoice date (the date you issue it) and the due date. A due date is clearer than a term alone: "Due 30 October 2026" leaves no room for interpretation, while "Net 30" leaves the client to work it out. Our guide to invoice payment terms explains the common terms and which to use.

6. List what you are charging for

Add one line per product or service. Each line needs a description, a quantity, a rate or unit price, and the line total (quantity multiplied by rate). Be specific: "Website work - $900" invites questions, while "Homepage redesign, 6 hours at $150" does not. If you bill by the hour, show the hours and the rate. If you bill a fixed fee for a project, name the deliverable and, where relevant, the period it covers.

For a long job, group lines under headings - Labour, Materials, Travel - so the client can see where the money goes.

7. Add the totals

Add up the line totals to get the subtotal. Apply any discount, then add shipping or other charges, then calculate tax on the amount you are actually charging. Finish with a clear total amount due, in bold, in the currency you are billing in. If the client has already paid a deposit, show it as a separate line and show the balance due.

8. Add payment terms and payment details

State when payment is due and exactly how to pay. For a bank transfer, give the account name, account number and the routing details the client needs: sort code in the UK, routing number in the US, IBAN and BIC for SEPA payments in Europe. Ask the client to use the invoice number as the payment reference, so you can match the payment when it arrives. If you accept card, PayPal, UPI, Zelle or another app, add a payment link or a payment QR code.

9. Add a short note

A one-line thank-you, a late-payment policy if you have one, or a note about what the invoice covers. Keep it short; this is not the place for terms and conditions that should have been agreed before the work started.

10. Check it, save it as a PDF and send it

Check the client's name, every figure and the total. Then save the invoice as a PDF rather than sending an editable Word or Excel file - a PDF looks the same on every device and cannot be changed by accident. Send it to the right person, ideally on the day the work is finished, and keep a copy for your records.

Invoice example

Here is a complete example of a simple service invoice. Use it as a model for your own.

INVOICE #2026-014
From: Sara Khan Design, 12 Park Road, Leeds LS1 4AB, hello@sarakhan.design		Bill to: Northwind Coffee Ltd, 88 King Street, Manchester M2 4WU
Invoice date: 1 October 2026		Due date: 15 October 2026
Description	Qty	Rate	Amount
Logo design - primary mark and wordmark	1	£850.00	£850.00
Packaging artwork - coffee bag, 3 variants	3	£220.00	£660.00
Additional revision round	2	£90.00	£180.00
Subtotal			£1,690.00
Total due			£1,690.00
Payment: Bank transfer to Sara Khan Design, sort code 12-34-56, account 12345678. Please use 2026-014 as the reference. Payment due within 14 days.

This example has no VAT because the designer is not VAT registered. A VAT-registered business would add its VAT number, the VAT rate and VAT amount for each line or in total, and the total including VAT.

How to make an invoice for free

You do not need paid software to send a professional invoice. The quickest free route is an online generator: open the invoice generator, fill in your details, your client and your line items, pick a design and download the PDF. There is no account and no watermark, and totals and tax are calculated as you type. If you work in a particular trade, start from a template that already has the right kind of line items - for example the freelance invoice template, the construction invoice template or the photography invoice template.

If you prefer a spreadsheet, build one master template with your details, formulas for the totals and a cell for the invoice number, then save a copy for each new invoice and export it to PDF before sending.

How to send an invoice

Email is the standard. Attach the PDF, put the invoice number and amount in the subject line - "Invoice 2026-014 from Sara Khan Design - £1,690 due 15 Oct" - and write two or three lines in the body: what the invoice is for, the total, the due date and how to pay. Send it from the email address your client already knows, so it is not caught by a spam filter. If the client uses a supplier portal, upload it there as well, because that is often the only place their accounts team looks.

What to do after you send it

• Track it. Keep a simple list of invoices sent, their due dates and whether they have been paid.
• Follow up on time. A friendly reminder a few days before the due date and another on the day after it is missed solves most late payments. Our overdue invoice email templates give you wording for each stage.
• Issue a receipt once you are paid if the client asks for one - you can make one with the receipt generator.
• Keep copies. Tax authorities generally expect you to keep invoices for several years - six years in the UK, for example.

Common invoicing mistakes

• No due date. Without one, many clients default to paying whenever their next payment run is.
• Vague line items. Anything the client has to ask about gets held until they have the answer.
• Missing payment details. Every email asking "how do I pay you?" adds days.
• Wrong or missing PO number for corporate clients.
• Duplicate invoice numbers, which confuse your records and the client's.
• Sending it late. Invoice the day the work is finished, not at the end of the month.

Frequently asked questions

Can I write an invoice if I am not a registered business?

Yes. Sole traders and freelancers who are not registered for VAT or GST can and should issue invoices. Use your own name (and any trading name), leave out tax fields you do not have, and do not charge tax you are not registered to collect.

Can I handwrite an invoice?

Legally, usually yes, as long as it contains the required information. In practice a typed PDF is faster to produce, easier to read and easier to keep records of.

Do I need an invoice number?

Yes. A unique number is required in most countries and it is how you and your client refer to the invoice when discussing payment.

What is the best format to send an invoice in?

PDF. It looks identical on every device, prints correctly and cannot be edited by accident.