How to write an invoice that gets paid
A good invoice answers every question before your customer has to ask it: who it is from, what it is for, how much, by when and how to pay. Here is how to write an invoice, section by section, wherever you work.
How to write an invoice: what every invoice needs
Rules differ between countries, and invoices that carry tax have extra requirements, but the core details are much the same everywhere. The UK government’s list is a sound baseline for any small business:
- A unique invoice number.
- Your business name, address and contact details, plus your legal name if you trade under a different one.
- Your customer’s name, or their business name, and their address.
- The date of the invoice, and the date you did the work if that is different.
- A clear description of what you are charging for, with quantities and prices.
- The amounts, any tax, and the total owed.
- When payment is due and how to pay.
Number every invoice once, in order
Invoice numbers let you, your customer and your tax office refer to one document without confusion. Use each number once and keep them in sequence. You can start wherever you like, such as INV-1001, and a prefix that marks the year or the brand keeps things tidy when you run more than one business.
Never reuse or delete a number after an invoice has gone out. If an invoice was wrong, cancel or credit it and issue a new one, so the trail stays complete. Some countries also set a format: India, for example, limits GST invoice numbers to 16 characters, unique for the financial year.
Describe the work so nobody has to ask
Vague lines are the most common reason an invoice sits unpaid while someone checks what it is for. Compare these two:
- Too vague: Plumbing work, $450.
- Clear: Replace kitchen mixer tap, supplied and fitted, 1.5 hours labour, 14 Oct, 22 Example Street.
- Put labour and materials on separate lines, so the customer sees what they paid for.
- Give quantities in units people understand: hours, visits, rooms, square metres or items.
- Add the customer’s purchase order or your quote number if they gave you one; some businesses cannot pay an invoice without it.
Get the tax right
If you are registered for GST, VAT or sales tax, show the rate and the amount of tax separately from the price, along with your tax number. Some countries also expect particular wording: Singapore and the United Arab Emirates require the words Tax Invoice, Australia asks that the document shows it is meant to be a tax invoice, and South Africa accepts tax invoice, VAT invoice or invoice. Our guide to what a tax invoice is compares the rules country by country.
If you are not registered, do not add tax or call the document a tax invoice. Charging tax you are not registered for creates a problem for you and for your customer.
Decide whether your prices include tax or have it added on top, then stay consistent across your quotes and invoices. When a job mixes items at different rates, make sure each line carries the right one.
Make paying easy
Write the due date as a date, such as Due 14 November 2026, rather than only Net 30, because nobody has to work it out. Then show every way to pay: your bank details in the format your country uses, a card payment link if you take cards, and the reference you want them to use, normally the invoice number.
If you took a deposit, show it as a deduction so the balance due is obvious. If you charge late fees or interest, say so in your terms before the work starts, not for the first time on an overdue invoice. Our guide to payment terms explains the options.
A worked example of a clear invoice format
A simple invoice from a photographer who is not registered for VAT, so there is no tax line. It still has a unique number, both parties, the date of the work, clear lines and a due date.
Example only, with a fictional business and customer. Your invoices use your own details, tax settings and design.
| Description | Qty | Rate | Amount |
|---|---|---|---|
| Event photography, half day (4 hours), 10 Oct 2026 | 1 | £480.00 | £480.00 |
| Edited high resolution images, digital delivery | 60 | £3.50 | £210.00 |
| Travel to venue, return | 1 | £35.00 | £35.00 |
Mistakes that slow payment down
- No due date, or only a vague one.
- A misspelt email address, so the invoice never arrives at all.
- Sending the invoice days or weeks after the job, when the customer has moved on.
- Editing an invoice after it was sent instead of issuing a credit and a fresh invoice.
- Missing bank details, or no payment reference, so the money arrives but nobody can match it.
- Adding tax when you are not registered, or leaving it off when you are.
How WhizInvoice fills this in for you
In WhizInvoice your business details, logo, tax number and bank details are saved once and appear on every invoice. Invoice numbers run in sequence by themselves, your saved prices are a tap away, and the country setting takes care of the tax name, rate and title.
When a job starts as an enquiry on your website, the customer’s name, email, phone and address carry straight into the invoice, so there is nothing to retype and nothing to misspell. See how in website enquiries, or start with the invoice template if you prefer to work by hand.
Good to know
Can I write an invoice in Word or by hand?
Yes, as long as it has the required details and a unique number. The risk with documents built by hand is repeated numbers, sums that do not add up and invoices nobody follows up.
How is an invoice different from a receipt?
An invoice asks to be paid. A receipt confirms that payment has already been received, usually after the invoice.
What number should my first invoice have?
Any number you like, such as INV-1001. What matters is that each number is used once and they run in order from there.
Can I change an invoice after I have sent it?
It is better not to. Issue a credit note for the wrong invoice and send a corrected one, so your records and your customer’s match.
Do I need to include my tax number?
If you are registered for GST or VAT, yes. Every GST and VAT country on our site expects it on tax invoices, though some only above a set amount, such as NZ$200 in New Zealand or C$100 in Canada. If you are not registered, leave the tax number and tax line off.
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