Part 1
Get these details together first
Writing the invoice is the quick part. What eats the time is hunting for things: the client's postcode, the date you finished, the price you agreed in a message three weeks ago. Gather them first and the invoice takes minutes.
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What was agreed
The quote, booking or message where the price was set. Your invoice should match it, or show where and why it differs.
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Who is paying
For a household client, that's normally the person you dealt with. For a business, get the registered name, billing address and the accounts team's email, which is often not the person who hired you.
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Any reference they need
Larger clients often won't pay without a purchase order (PO) number or cost code. Ask before you start, because learning about it when the invoice comes back can push payment into the next month's run.
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The dates
When the work was finished, or for ongoing work the period it covers, such as 1 to 30 September.
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Your tax position
If you're registered for VAT or GST, you'll usually need to charge it, and the invoice has to show extra details such as your registration number and the tax charged. If you aren't registered, you generally can't add it. In the US, sales tax depends on the state and on what you sell. Your tax authority (HMRC in the UK) sets out what applies to you.
Part 2
The parts of an invoice, from top to bottom
Whoever checks your invoice will look for the same things in roughly the same places, so put them where they expect to find them. This is the usual layout from the top of the page down.
In many countries some of these details are a legal requirement, and the exact list depends on the country and your tax registration. In the UK, GOV.UK has a short page on what an invoice must show; elsewhere, check your tax authority's invoicing rules.
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The word "Invoice"
Put it at the top. A document headed "Quote" or "Estimate", or with no heading at all, may get filed instead of paid.
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Your details
Your name and any trading name, address, email and phone, plus your VAT or company number if you have one.
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The client's details
Their name exactly as it appears on the quote or purchase order, the billing address, and the PO number if there is one.
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Invoice number
A number of its own that follows on from your last. Both of you will quote it if the invoice ever comes up again.
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Three dates
The invoice date, the date or period of the work, and the due date written as a calendar date so nobody has to count days.
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Line items
One row per piece of work: description, quantity, unit (hour, page, visit, day), rate and line total. Materials, travel and extras get rows of their own.
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Totals
Subtotal, then any discount, then tax if you charge it, then the total. If a deposit was paid, list it with its date and end on the balance owed.
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Payment details and terms
How to pay, which reference to quote and by when. If you mention late payment charges, stick to ones the client agreed before the work began or that the law already gives you.
Part 3
A worked example, laid out as plain text
Below is a complete invoice from a freelance graphic designer who isn't VAT-registered, billing a company for a product brochure. It will be checked by someone in the accounts team who has never spoken to the designer, so everything they need is on the page. Swap in your own details and the same layout works for a cleaning job, a boiler service or a photo shoot.
The first line names the quote the work came from, which lets the accounts team match the invoice to what they approved. The extra round of amends wasn't in that quote, and an unexplained extra is one of the commonest reasons for a query, so its line records when and how it was approved. With the stock photos priced per image, anyone can check the £48 in their head.
The "Not VAT registered" line is optional. Some sole traders add it so a bookkeeper doesn't assume VAT was left off by mistake.
INVOICE From [Your name], trading as [Your trading name] [Street address], [Town] [Postcode] [Email] · [Phone] Bill to [Client's registered business name] Accounts department, [Billing address] PO number: [PO number the client gave you] Invoice number: INV-0042 Invoice date: 16 October 2026 Work completed: 14 October 2026 Due date: 30 October 2026 1. Product brochure design, 12 pages, as quoted on 18 September (quote Q-0031) 1 project × £900.00 = £900.00 2. Extra round of amends, not in the quote, approved by email on 8 October 3 hours × £40.00 = £120.00 3. Stock photos licensed for the brochure, charged at cost 4 images × £12.00 = £48.00 Subtotal: £1,068.00 Total due: £1,068.00 Not VAT registered. How to pay Bank transfer to: Account name: [Name exactly as your bank holds it] Sort code: 00-00-00 Account number: 00000000 Reference: INV-0042 Payment terms: 14 days from the invoice date. My bank details will never change by email. If you're asked to pay a different account, call [phone] first. Thank you for your business.
Part 4
Writing payment details clients can use first time
The client copies this section straight into their banking app, so check it as carefully as you'd check the address on a parcel. A single wrong digit can hold the payment up for days, or leave the client emailing you to confirm before they'll send anything.
In the UK, banks compare the name a payer types in with the name on the receiving account when a new payee is set up, and banks in the euro area now run a similar check on euro transfers. Give the account name exactly as your bank holds it, which for many sole traders is their personal name. If it doesn't match, the client sees a warning, and a careful accounts team will hold the payment until you've explained.
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Bank transfer in the UK
Account name, sort code, account number and a reference. Use the invoice number, since that's what you'll search for on your statement.
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Clients in other countries
Add your IBAN and BIC (or SWIFT code), give the currency code, such as GBP, and agree who pays transfer charges so the amount that lands matches the invoice.
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Card payments
If you take cards through a payment provider, put the payment link on the invoice and in the email so a household client can pay from their phone.
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Cash and cheques
Say who cheques are payable to, using the name your bank account is in, and give a receipt whenever you take cash.
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A line about changed details
A common scam is an email, apparently from you, giving the client "new" bank details. A sentence saying yours will never change by email costs nothing and gives a careful client a reason to ring you first.
Part 5
Why invoices get queried, and how to head it off
When a client has a question about an invoice, payment stops until it's answered, and by then the payment run it would have made may have gone. These are the causes that come up most.
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The total doesn't match the quote
If the job grew, keep the original price as its own line and add each extra separately, noting who approved it and when.
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No PO number or cost code
Many businesses match every invoice to a purchase order before paying. Without the number, yours waits until somebody works out who ordered the work.
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You're not on their supplier list yet
Plenty of companies won't pay a first invoice until you've been set up on their system, which usually means filling in a supplier form and proving your bank details. Ask for the form when you're hired, not when the invoice falls due.
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Sums that don't add up
Check each line's quantity times rate, and that the lines add up. With tax, round consistently; whoever reconciles it will spot a total that's a penny out.
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VAT that shouldn't be there
In the UK only VAT-registered businesses can charge VAT, and a VAT invoice must show your VAT number. If your registration is still going through, leave VAT off for now; GOV.UK explains how to reissue those invoices once the number arrives.
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Regular work with no dates
"Cleaning, October" leaves the client guessing which visits they're paying for. List the dates, or attach a short log if there are many.
Part 6
Sending the invoice and keeping track of it
Send the invoice when the job is finished, or on the agreed day for regular work. Terms usually run from the invoice date, so each day you wait pushes your payment back too.
Send a PDF with a findable file name, such as "INV-0042 [Your trading name].pdf", and put the number, amount and due date in the email itself. If the client has an accounts address, send it there and copy in your usual contact.
Keep a list of what went out and when each one is due. If a due date passes with nothing in the bank, a short, polite reminder the next working day is the usual first step.
If you write invoices in Invooza, each one is numbered as you create it, a saved client fills in the Bill To block, and items from your products and services list come in with their description and price. A PO number can be set up as a custom field, so it prints on the PDF. You then email the invoice from your invoice list with the PDF attached, and mark it paid there when the money lands.
Subject: Invoice INV-0042, £1,068.00, due 30 October Hi [name], Invoice INV-0042 is attached for the product brochure design, quoted on 18 September and delivered on 14 October. Amount: £1,068.00 Due: 30 October 2026 PO number: [PO number] Payment is by bank transfer to [account name], sort code 00-00-00, account 00000000. Please use INV-0042 as the reference. If anything on it needs checking, reply here and I'll get back to you the same day. Thanks, [Your name] [Phone]
FAQ
Frequently asked questions
Can I write an invoice in Word or Excel?
Yes, plenty of sole traders start that way. Save it as a PDF before sending so it looks the same on every screen and can't be edited by accident, and keep a list of the numbers you've used so none repeats. Once you're sending more than a handful a month, an invoicing tool saves retyping and adding up by hand.
Do I need a business name to send an invoice?
No. In the UK and many other countries a sole trader can invoice in their own name. If you do use a trading name in the UK, the invoice also needs your own name and an address where legal documents can reach you. Keep the account name in your payment details as the one your bank holds.
What's the difference between a quote, an invoice and a receipt?
A quote is the price you offer before the work. An invoice asks for payment for work done or agreed. A receipt confirms you've been paid. When a client pays on the spot, an invoice marked as paid can do the job of a receipt.
What should I do if I've sent an invoice with a mistake on it?
Tell the client either way. For a slip that doesn't change what's owed, such as a misspelt name or a missing PO number, a corrected copy clearly marked as a replacement is usually enough. If the amount or the client is wrong, cancel the original with a credit note and issue a new invoice with the next number. If you're VAT-registered, check your tax authority's guidance first.
How soon should I send an invoice after finishing a job?
The same day or the next working day is a good habit. For regular clients billed monthly, pick a fixed day, such as the last working day of the month, so they know when to expect it.