@3T We should try it out with abolishing corporation tax first. The benefit to changing to an addition or extension of the sales tax on everything - from cups of coffee through to a new car or house and including a micro-tax on every financial transaction ( Tobin Tax) would be that the exchequer would definitely get a share of all goods and services sold by multinationals in this country, unlike at present, where multinationals take advantage of all sorts of loopholes in corporate law and revenue regulations to avoid income tax.
Personally, I think that would bring billions more into the exchequer and would save HMRC a fair bit in revenue collection costs.
But before you abolish direct taxation and do away with HMRC completely, you need to be very sure that you have a mechanism in place that will reliably bring in more income than currently, and does not cost us more than the £4billion a year that HMRC currently costs us.
You would have to demonstrate that such a switch was not regressive- ie that the vast majority of tax-payers, those only paying the standard rate, were not financially disadvantaged as a result of any proposed change, and no one has been able to offer any figures on that yet. And it still does not to address the massive imbalance between the vanishingly small number of people who control the majority of the worlds wealth and resources.
If it were up to me, I would advocate the abolishment of corporation tax as a first step, to be replaced with a flat sales tax of, say 9% on sales of everything within the UK to go the exchequer. (corporation tax currently raises around 8% of total revenue to the exchequer), including a micro-tax on all inter-bank and share dealing transactions (Tobin Tax).
And, rather than just raise the threshold at which taxpayers pay 40%, I would instead just raise the tax-free earnings threshold more agressively, since this would benefit all taxpayers, not just the better-off.