Invoicing basics
How to write an invoice
Every invoice does two jobs: it tells the customer exactly what they owe, and it gives you something enforceable if they do not pay. Here is the order we would write one in.
1. Head it clearly
Write the word Invoice at the top. It sounds trivial, but a document headed "quote" or nothing at all gets treated as optional by accounts departments. Underneath, put your business name, address, phone, email and — if you have them — your company number and VAT number.
2. Give it a unique number and two dates
Every invoice needs a unique identifying number, and never reuse one. Keeping them in a single running order is good record-keeping rather than a requirement on every invoice, though VAT invoices carry extra numbering requirements. Then show the invoice date (when you raised it) and the due date as an actual date, not "14 days". A real date removes the argument about when the clock started.
3. Say who it is to
Name the person or company legally responsible for paying, not just the site. On commercial work that is usually the registered company name plus their purchase order reference — miss the PO and the invoice sits unpaid in a queue.
4. Itemise the work
One line per item of labour or materials, each with a quantity, unit price and line total. Split labour from materials if the job falls under CIS, because deductions only apply to the labour element.
- Labour — 2 days first fix, £280/day, £560
- Materials — 22mm copper, fittings, £143.60
- Waste removal — £45
Vague lines like "works as agreed" invite disputes. Detail is what makes an invoice hard to argue with.
5. Show the money in three parts
Subtotal, VAT (if you are registered, with the rate shown), then the total due. If the domestic reverse charge applies, no VAT is charged but you still state the rate the customer must account for.
6. Payment details and terms
Bank name, account number and sort code, plus what reference to use — normally the invoice number. Add your terms line: what happens if it is late, and whether you charge statutory interest.
7. Send it the same day and keep the record
Email a PDF while the work is fresh in the customer's mind, and keep a copy for six years. Sending late is the single most common reason trades get paid late.
Common questions
Do I need to be VAT registered to send an invoice?
No. Anyone trading can invoice. If you are not VAT registered you simply do not add VAT and you do not show a VAT number — never show a VAT line if you are not registered.
What should I number my first invoice?
Anything works as a start, for example 0001 or 2026-001. GOV.UK says an invoice must carry a unique identifying number. Running them in order is simply good record-keeping rather than a rule for every invoice, though VAT invoices have additional numbering requirements for the sequence you use. Never reuse a number.
How long should I give a customer to pay?
For domestic work, payment on completion or 7 days is normal. For commercial and contractor work, 14 or 30 days is common. Between businesses, where no term is agreed, the default payment period under the late payment rules is 30 days — that default does not apply to ordinary consumer work, so always state your terms.
Can I invoice as a sole trader without a company number?
Yes. Sole traders show their own name, any trading name and a contact address. Company numbers are only required for registered limited companies.
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