An invoice is just a request for payment. But a few details are required by law, and a few more make the difference between being paid this week and being paid next month. Here's the whole list, in plain English.
What every invoice must include
| Item | What it means in practice |
|---|---|
| A unique invoice number | Every invoice gets its own number and you never reuse one. A simple sequence (001, 002, 003…) is easiest to follow. |
| Your name and business details | As a sole trader: your own name, plus your business name if you use one, your address and how to contact you. If you trade under a business name, you must also give an address where legal documents can reach you. |
| Your customer's name and address | Their company name if they're a business. |
| The invoice date | The day you issue it. |
| The date of the work | When you did the job or delivered the goods (the "supply date"). |
| A clear description | What you did or supplied. "Kitchen refit, 14 Oak Road: labour 5 days, materials as quoted" beats "Work done". |
| The amounts | The price of each item and the total amount owed. |
What it should include to get you paid faster
A due date, written as a date. "Payment due by 31 October" is clearer than "30 days", and much harder to "forget".
How to pay you. Your bank account name, sort code and account number, and what to use as the payment reference (the invoice number works well). Make paying you effortless.
Your terms, briefly. One line such as "Payment due within 14 days. Late payments may be charged interest under the Late Payment of Commercial Debts Act." is enough for business customers.
If you're VAT-registered (and if you're not)
Not VAT-registered? Then you must not charge VAT or show it on your invoices. Most new sole traders aren't: you only have to register once your turnover goes over £90,000 in any rolling 12 months.
VAT-registered? Your invoices must be proper VAT invoices, which add your VAT registration number, the VAT rate and amount of VAT for what you've charged, and the totals both before and after VAT. Your VAT-registered customers need these details to reclaim the VAT.
A word about numbering
People worry about this more than they need to. The rules are simple: each number is used once, and you can explain the sequence. If you cancel an invoice, don't delete it and reuse the number. Keep it, marked as cancelled, or issue a credit note against it. A gap-free, unedited trail is exactly what an accountant or an HMRC check wants to see.
When a business customer pays late: your legal rights
If your customer is a business (not a private individual), UK law gives you three things, even if you never mentioned them in advance:
1. A default deadline. If you didn't agree a payment date, payment is late 30 days after the customer received your invoice (or after you did the work, if that was later).
2. Interest. You can charge interest of 8% a year plus the Bank of England base rate on the overdue amount.
3. A fixed fee for chasing, once per invoice:
| Amount owed | You can add |
|---|---|
| Up to £999.99 | £40 |
| £1,000 to £9,999.99 | £70 |
| £10,000 or more | £100 |
You don't have to use these rights, and with a good customer who's simply disorganised you might not want to. But mentioning them politely in a second or third reminder tends to move an invoice to the top of the pile. These rules don't apply to private customers (households); for them, your agreed terms are what count.
Three habits that get invoices paid
Invoice the day the job ends, while the customer is still pleased with the work.
Send it by email as a PDF, so it can't get lost in a van or a kitchen drawer, and you have a record of when it arrived.
Chase early, politely and in writing. A friendly reminder a few days before the due date, another on the day, and a firmer one a week later catches most late payers without an awkward phone call.
In Invoice4You, invoice numbers are generated for you in sequence, your business and bank details go on every invoice automatically, and you can switch on up to three automatic reminder emails, so the chasing happens without you.
Sources: GOV.UK, Invoices: what they must include; GOV.UK, Late commercial payments: charging interest and debt recovery and claiming debt recovery costs; HMRC, VAT registration: when to register. This is general information, not legal or tax advice.