Send the invoice, wait, chase. Most sole traders and small limited companies know that routine well. What catches people out is how often a payment stalls not because the work was poor or the client is slow by nature, but because the invoice itself was missing a purchase order reference, a VAT figure or a due date that someone in accounts could actually act on.
Getting the details right takes ten minutes the first time and saves a fortnight of polite reminder emails afterwards. Here is what a UK invoice should contain, what changes once you are VAT registered, and where people most often slip up.
The details every UK invoice should carry
For a sole trader who is not VAT registered, UK law is lighter than most people assume. No single statute lists every field. But an invoice that a client's finance team can process without picking up the phone will always include the following:
- The word Invoice as a heading, so it cannot be mistaken for a quotation or a statement
- A unique invoice number, issued in sequence and never reused
- The date the invoice was issued, and the date the supply was made if the two differ
- Your business name and the address you trade from
- The customer's name and address, matching the entity that will actually pay
- A clear description of the work or goods, with quantities and rates
- The amount due in pounds sterling, stating whether VAT is included
- Payment terms and a specific due date
- Bank details, including a reference that helps the client match the payment to you
- Any purchase order, job or contract reference the client gave you
Plain detail beats clever design. A line reading "Website redesign, 12 hours at £45 per hour, as per quotation dated 3 March" tells an accounts clerk everything. A line reading "Consultancy" invites a query.
Extra requirements for limited companies
If you trade through a limited company, company law requires certain information to appear on business correspondence, and an invoice counts. In practice, a limited company invoice should show:
- The company's registered name, not just a trading name
- The company registration number
- The place of registration — England and Wales, Scotland, or Northern Ireland
- The registered office address
If you trade under a name that differs from the registered one, make the relationship obvious, for example "Ridgeway Joinery Ltd, trading as Ridgeway Kitchens". Limited liability partnerships have similar disclosure obligations. Directors sometimes only discover this during a bank review or a dispute, which is an uncomfortable moment to fix it.
VAT invoices: what to add
Once you are VAT registered, the invoice stops being just a request for payment and becomes a tax document. A full VAT invoice must include:
- A unique, sequential invoice number
- The time of supply, or tax point, if it differs from the invoice date
- Your business name, address and VAT registration number — usually a nine-digit number prefixed with GB
- The customer's name and address
- A description of what you supplied
- The quantity and unit price, excluding VAT
- The rate of VAT charged on each line: 20%, 5% or 0%
- The total excluding VAT
- The total VAT amount
- The total including VAT
For supplies totalling £250 or less including VAT, a simplified invoice is permitted. It needs less detail, but your VAT number, the date, a description and the rate charged must still appear. Many retailers selling to the public use these.
Two warnings worth remembering. You cannot charge VAT unless you are registered, and you must never show a VAT number that is not yours. If you are unsure whether a particular supply is standard-rated, zero-rated or exempt, take advice before the invoice goes out. Correcting it afterwards means issuing a credit note and starting the paperwork again, and your customer has already waited.
Common omissions that delay payment
Most late payments are administrative, not deliberate. These are the gaps that send an invoice back into the system:
- No purchase order number. Larger organisations often cannot pay without one, and the invoice is simply parked.
- Vague payment terms. "Payment within 30 days" is open to interpretation. "Due 15 June" is not.
- Wrong customer entity. Invoicing a trading name when the contract sits with a different company can mean a rejection and a reissue.
- Gaps or duplicates in numbering. Finance teams read irregular sequences as a sign of duplicate billing.
- Bank details buried or missing. Put them in the same place on every invoice.
- No VAT number on a VAT invoice. Without it, the customer cannot reclaim input VAT and will ask for a corrected copy.
- Sent to the wrong inbox. The person who commissioned the work is rarely the person who runs the payment.
- Unreadable format. A photograph of a handwritten invoice rarely survives a scanning system intact.
Small habits that speed things up
Invoice the day the work is delivered, or on the agreed milestone, rather than at month end. Agree terms in writing before you start, and put them on the invoice itself. Include a remittance email address so clients can tell you when they have paid.
If a commercial customer misses the agreed deadline, the Late Payment of Commercial Debts (Interest) Act 1998 gives you a statutory right to claim interest, set at 8% above the Bank of England base rate, plus a fixed compensation sum that depends on the size of the debt. It also implies a 30-day payment term where none has been agreed. Many businesses never invoke it, and that is a reasonable commercial choice, but knowing it exists changes the tone of a follow-up email. Check current rates before relying on them.
Chase politely and on a schedule: a reminder on the due date, a second a week later, a phone call after that. Keep it factual and reference the invoice number.
A quick checklist before you press send
- Is the invoice number unique and in sequence?
- Are your business name, address and VAT number correct and current?
- Does the customer name match the entity that will pay?
- Is there a due date, not just a payment term?
- Are the bank details right, and is the payment reference included?
- Have you attached or referenced the purchase order?
- Does the description explain what was supplied and when?
None of this is glamorous, and none of it takes long. But a well-built invoice is the difference between being paid quietly and being paid after four emails and a phone call. This is general guidance rather than legal or tax advice; VAT treatment and company disclosure rules depend on your own circumstances, so speak to an accountant or check with HMRC if anything is unclear.
