How to Invoice a Customer Properly

What has to be on it

There is no single 'invoice template' mandated by law in the UK, but there is a settled set of information that customers and HMRC expect to see. Once you are VAT registered, the rules become stricter and a smaller set of information becomes legally required.

Getting the basics wrong — a missing invoice number, an ambiguous due date, or omitting your VAT number when you should show one — hands a slow-paying customer a legitimate reason to query the invoice. A query resets the clock. An invoice sent on the 1st with a 30-day term, queried on the 28th because the bank details were missing, and reissued on the 29th, is not going to be paid until day 60. The administrative detail is what protects your cash flow.

• Your business name, address and contact details.
• The customer's name and address.
• A unique, sequential invoice number (e.g., INV-2026-001).
• The date of the invoice and the date the goods or services were supplied (the 'tax point').
• A clear, itemised description of what was supplied.
• The amount charged, VAT if registered (rate and amount shown separately), and the total due.
• Your VAT registration number, if you are registered.
• Your company registration number, if you are a limited company.
• Payment terms and the exact due date, not just 'net 30'.
• How to pay: clear bank details or a clickable payment link.

Terms that get paid, not just terms that look professional

'Payment due within 30 days' is standard across much of the UK economy, but it is a starting point, not a rule you have to accept. Shorter terms — 7 or 14 days — are entirely normal for smaller jobs, independent contractors, and new customers. Most customers will not push back if you simply state your terms clearly from the outset.

The language you use on the invoice matters. A specific due date beats a duration every time. Writing 'Due by 14 March 2026' leaves no room for a customer's accounts department to argue about whether the 30-day clock started when you sent the invoice, when they opened the email, or when they processed it into their system. Also, state your bank details or include a payment link on every single invoice, not just the first one. Customers lose details, and asking you to resend them is another excuse for delay.

Invoice on completion, not at month end

Batching invoices to send them all on the last day of the month is a common administrative habit that quietly costs small businesses weeks of cash flow. If a job finishes on the 3rd of the month but you wait until the 30th to invoice it, you have voluntarily added nearly four weeks to your own payment terms before the customer has even seen the bill.

Invoicing on the day the work is delivered — or as specific milestones are reached on longer projects — is one of the few genuinely free improvements to cash flow available to a small business. It requires no negotiation with the customer and no change to your pricing; it only requires a change to your own routine.

Make paying easy

Every extra step between a customer deciding to pay and the money actually leaving their account increases the chance of delay. A plain PDF invoice attached to an email requires the customer to log into their banking app, set you up as a new payee, carefully type in the amount, and hit send. That is enough friction for them to decide to 'do it later'.

Including a payment link (like Stripe or GoCardless) or a card payment option alongside your bank transfer details removes that friction. Yes, you will pay a small percentage fee for card processing, but getting paid 14 days faster is often worth the fee, particularly if it saves you the administrative time of chasing.

What to do, in order

1. 1

   Invoice on the day work finishes

   Or on agreed milestones for longer jobs. Do not wait for the end of the month to do an administrative batch.

2. 2

   Use a sequential invoice number

   This makes chasing and reconciling straightforward for both sides, and is legally required if you are VAT registered.

3. 3

   State a specific due date

   Write 'Due by 17 March' rather than 'net 14' or 'payment within 14 days'.

4. 4

   Include a payment link or clear bank details

   Put this information on the invoice itself, every single time you send one.

5. 5

   Send it to the right person

   Check who actually approves the payment, especially for business customers with a separate accounts payable function. Sending it to the person who commissioned the work is often the wrong route.

6. 6

   Confirm receipt early

   A short, polite message a few days after sending, asking if the invoice arrived and looks correct, catches queries early while there is still time to fix them before the due date.