So Saint Vince is prepared to sacrifice the 50p tax rate for a mansion tax. The mansion tax would be directed at those with houses with a value of over £2 million and, as houses cannot be hidden in offshore accounts, the tax should be relatively easy to collect.
Well yes and no. The mansion tax would first of all require a database of all houses worth over £2 million. The Inland Revenue do not have such a database; nor do local authorities. It would therefore have to be compiled from scratch, a fairly mammoth task which would require the commissioning of a multitude of surveyors and valuers. It would also be necessary to identify the owners of the houses concerned, and of course to enable them to appeal the valuations where appropriate. All this would require primary (and probably secondary) legislation. So it would take at least a couple of years to implement.
I'm not saying that this should not be done, only questioning whether Vince and his ilk have thought it through. By comparison, the abolition of the 50p tax rate is utterly straightforward.