The various software packages that HMRC use are vast and very clever/powerful and as DH says are very good at estimating things.
Their first port of call when examining a boiler that has been registered with Gas Safe, in relation to someone they are investigating, would be to see if there has been an invoice raised at all, or a corresponding payment into ones bank account, not necessarily any amounts.
I would imagine someone doing a cash boiler install would have nothing to reconcile with his books or accounts.
As soon as computers are used, there is always an auditable trail, for use by anyone who has the knowledge or determination to utilise it.
Their first port of call when examining a boiler that has been registered with Gas Safe, in relation to someone they are investigating, would be to see if there has been an invoice raised at all, or a corresponding payment into ones bank account, not necessarily any amounts.
I would imagine someone doing a cash boiler install would have nothing to reconcile with his books or accounts.
As soon as computers are used, there is always an auditable trail, for use by anyone who has the knowledge or determination to utilise it.