This is a type of tax evasion that happens when you do not charge VAT when you are supposed to, or you charge VAT and fail to pay it to HMRC. HMRC may investigate VAT fraud reported or suspected if you have: requested a customer pay by cash, asked the customer to pay someone else or another account other than your business, not registered for VAT when it is believed you should have, claimed to have applied for a VAT number but have not, or used an invalid VAT number.