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

An invoice is a formal request for payment. It tells your client what they bought, how much they owe, when the money is due and how to pay it. A clear invoice gets paid faster, survives an accountant’s scrutiny and protects you if there is ever a dispute.

This guide walks through writing an invoice from a blank page, step by step, with a worked example at the end. If you would rather fill in a form, the free invoice generator follows exactly the same structure and gives you a PDF when you’re done.

What an invoice needs to do

Before getting into fields and layout, it helps to know what a good invoice actually achieves. It should let anyone — your client, their accounts payable team, your accountant or a tax inspector — answer five questions without having to email you:

1. Who is billing whom? (seller and buyer, with legal details)
2. What was supplied? (goods or services, quantities, prices)
3. When was it supplied, and when was it invoiced?
4. How much is owed, including any tax?
5. How and by when should it be paid?

Every step below serves one of these questions.

Step 1: Put your business details at the top

Start with your own information, usually in the top-left or top-right corner:

• Your business or trading name (and your legal name if different — a sole trader trading as “Blue Fern Design” should usually show their own name too)
• Postal address
• Email and phone
• Tax registration number if you have one (VAT number, GST number, ABN, EIN where relevant)
• Company registration number, if you are a registered company and local rules require it
• Your logo, if you have one — optional, but it makes the document instantly recognisable

Step 2: Add the client’s details

Directly below or opposite your details, add who the invoice is addressed to:

• The client’s legal business name (not just the contact person)
• Their billing address
• A contact name or department (“Accounts Payable”) if they have asked for one
• Their tax number, if you are invoicing a business in a system where it’s required — for example, intra-EU reverse-charge invoices must show the buyer’s VAT number

Tip: ask new clients for their exact billing details before you send the first invoice. A large company may reject an invoice that is addressed to the wrong legal entity or is missing a purchase order (PO) number.

Step 3: Label it clearly and give it a unique number

Write the word “Invoice” prominently at the top. If it’s a tax invoice in a country that uses that term (Australia, New Zealand, India and others), label it “Tax Invoice”.

Then give it an invoice number. Invoice numbers must be unique and should be sequential — most tax authorities expect an unbroken series. A simple, robust format is INV-2026-0001, INV-2026-0002, and so on. Our invoice numbering guide covers formats, multiple series and what to do if you skip or cancel a number.

Step 4: Add the dates

Most invoices need at least two dates:

If you’re unsure what terms to use, read payment terms explained.

Step 5: List the goods or services as line items

This is the heart of the invoice. Each line should have:

• Description — specific enough that someone who wasn’t in the room understands it. “Website work” is weak; “Homepage redesign — 3 layout concepts + 2 revision rounds” is strong.
• Quantity — hours, days, units, words, or simply 1 for a fixed-price item
• Unit price — the rate per unit, before tax
• Line total — quantity × unit price

Group related work, but don’t collapse everything into one vague line. Detailed lines answer questions before they’re asked, and questions are the most common reason an invoice sits unpaid.

Step 6: Calculate subtotal, discounts, tax and total

Work down from the line items:

1. Subtotal — the sum of all line totals
2. Discount — if any, shown as a separate negative line so it’s visible
3. Tax — VAT, GST or sales tax, calculated on the taxable amount and shown with its rate (e.g. “VAT 20%”)
4. Shipping or other charges, if applicable
5. Total due — the amount the client should pay, with the currency clearly stated

If you are not registered for VAT/GST, don’t charge it. Many countries require small, unregistered businesses to include a note explaining why no tax is charged (for example, a small-business exemption statement). See how to charge VAT on invoices and sales tax on US invoices for the details.

Step 7: Explain how to pay

Make paying you effortless:

• Bank transfer details (account name, IBAN/account number, BIC/SWIFT or routing number)
• Any payment link or accepted card/PayPal option
• The reference the client should use — normally the invoice number
• Who pays transfer fees on international payments, if relevant

Step 8: Add terms and notes

The footer is the place for:

• Payment terms (“Payment due within 14 days of the invoice date”)
• Late payment terms, if your contract or local law allows them (interest or a fixed fee)
• Required legal statements (e.g. “Reverse charge” notes, tax-exemption wording)
• A short thank-you — it costs nothing and reads well

Step 9: Check, save as PDF and send

Before sending, run through this checklist:

• Client’s legal name and address are correct
• Invoice number is unique and follows on from the last one
• Dates are correct and the due date is explicit
• Every line has quantity, unit price and line total, and the maths adds up
• Tax rate and amount are correct (or the reason for no tax is stated)
• Currency is stated
• Payment details are complete and correct
• Any PO number or reference the client requested is included

Send invoices as a PDF, not an editable document — it looks professional, prints consistently and can’t be accidentally changed. Name the file usefully, such as INV-2026-0042_BlueFernDesign.pdf, and send it to the person or address responsible for paying, not only your day-to-day contact.

Worked example

Here is a complete invoice from a UK-based designer who is VAT-registered, billing a UK client:

Footer: “Please pay by bank transfer to Blue Fern Design Ltd, sort code 00-00-00, account 12345678, using reference INV-2026-0042. Thank you for your business.”

(Bank and tax numbers above are placeholders.)

Common mistakes to avoid

• Vague descriptions. They invite questions and delay payment.
• No due date. “Payable on receipt” is often treated as “whenever”. Give a date.
• Reusing or skipping numbers without a record. It creates audit headaches.
• Charging tax you’re not registered for — or forgetting tax you are required to charge.
• Editing an invoice after sending it. If something was wrong, issue a credit note and a corrected invoice instead of silently changing the original.
• Sending it to the wrong person. Ask who processes invoices on the client side.

Invoice vs. quote vs. receipt

An invoice is sent after (or at agreed milestones of) the work, asking for payment. A quote is sent before, proposing a price; a receipt is sent after payment, confirming it was received. If you need one of those instead, use the quote generator or the receipt generator, and see invoice vs. receipt for the differences.

Invoice requirements vary by country, especially for VAT/GST-registered businesses. This guide covers widely used good practice and is not legal or tax advice — check your local rules or ask an accountant. Our invoice templates by country summarise common local requirements.