You must keep a record of everything that will have an impact on the amount of VAT that you need to pay. This includes: Everything that you buy and sell, even if it is VAT exempt or zero rated. Copies of every invoice issued. Copies of every invoice you receive. Details of any self-billing agreements – these are where a customer prepares the invoice themselves. Details of any self-billing suppliers including their VAT number. All debit and credit notes that were issued. Details of any goods that have left stock but not been paid for. It is a good idea to also retain all general business records including cheque books, paying-in books/slips, till rolls, bank statements and so on.