As self employed you would have to produce the data on the receipt to your accountant. He / She will interpret that in a way to meet whatever your business obligations are. If you do not have a business account, Apple would be unlikely to do more. The actual VAT amount is easily calculated.
Send in a ticket here:
iTunes Store Support
They have the opportunity to send you invoices, especially VAT type. You may wish to give them your VAT number though, as without it that may default the purpose.