Start with the document details
For a standard full VAT invoice, review the unique invoice number, supplier details and VAT registration number, customer details, invoice date and supply date. Describe the goods or services clearly, with the relevant quantities, prices, rates and totals. Different invoice types have different requirements; consult Notice 700.
Check the arithmetic separately
Multiply quantity by unit price, apply the agreed discount, then calculate VAT on the appropriate net line. Reconcile the net total plus the VAT total to the final amount due. Separate mixed-rate items rather than forcing one rate onto the whole invoice.
A practical example
Two net lines of £80 and £50, both at 20%, produce £16 and £10 VAT. Total net is £130, VAT is £26 and gross is £156. If a customer queries £156, you can show both the quantity calculation and the tax calculation rather than only a final total.
Before you send
Verify customer and supplier details against your records. Check special wording or treatment where relevant, and retain the final document. The calculator creates figures only; it does not generate a compliant invoice or validate a VAT registration number.
Keep learning
FAQs
What must a full VAT invoice show?
A full VAT invoice needs: a unique sequential invoice number, your business name, address and VAT number, the date of issue and the time of supply (if different), the customer's name and address, a description of the goods or services, the quantity and unit price excluding VAT, the VAT rate for each item, the total excluding VAT, and the total VAT charged.
When must I issue a VAT invoice?
You must issue a VAT invoice whenever you sell to another VAT-registered business (and keep a copy). The invoice should normally be issued within 30 days of the supply. For retail sales to the public, you only need to issue one if the customer asks.
What is a simplified VAT invoice?
For retail sales of £250 or less including VAT, you can issue a simplified invoice showing fewer details: your name, address and VAT number, the date, a description of the goods or services, the total payable including VAT, and the VAT rate(s) applied — with the total VAT implied by the rate.
Can I show VAT in another currency on an invoice?
You can show amounts in any currency, but the VAT amount itself must also be shown in sterling, converted at an accepted exchange rate (such as the Bank of England rate or the customs rate for the period).
How long do I keep copies of invoices?
Keep copies of all sales and purchase invoices for at least 6 years. They are the evidence for the figures on your returns and for any VAT you reclaim.
Official sources
Sources checked: 2026-09-26. Check the official guidance for later changes.
Educational information and estimates. These tools do not submit VAT returns or determine the treatment of a specific transaction.