VAT no. on Invoices is showing as xxxxx although I have added it to VAT Settings correctly. Could this be due to being on FRS VAT that it doesn't recognise it ?

Hello John, 

Welcome to the Community page,  

Can you clarify where you are exactly looking is it in the customer form syles section where you are seeing the vat number on the invoice as XXXX or is it on the invoice its self in the print/preview section?

Could you send us a screenshot of the page you are looking at so we can check it for you?