HMRC's guide to issuing a valid VAT invoice is available here.
As part of our formation and set up process we’ll be more than happy to check the formats of your invoices - it’s important to get invoices right, so we can let you have compliant samples to copy.
Your business’s VAT number may not have arrived when you raise your first sales invoices. In which case, submit an invoice to your client for the amount without VAT and include the description “VAT to follow” where the VAT number would normally appear. When the VAT Certificate does arrive issue a separate “VAT only” invoice for each customer to cover the VAT to date.
VAT must be charged on almost all goods and services, including any expenses that your business may have incurred that are being charge on to your customers.
We have a ready made invoice here in our Downloads section. Feel free to use it or modify it.