A quick thought:
Given that every rise in the personal allowance these days is met with an equivalent drop in the level at which the 40% rate kicks in (can’t have the rich benefiting, can we?), the logical extension of this policy is that the two will meet at around the £25,500 mark and the 20% band will completely disappear.
Libertarian Home 
It is all mad.
LikeLike
That would be “super”: average income in the UK is exactly 4k below that level, 21k/year. The majority of the electorate will fully support it and it is kind of “cool”: some 60%+ of the society will pay no income tax at all and can outvote these “damn neo-liberal supporters of the lower taxation”. The income tax will be paid entirely by us, stupid foreigners and these who earn 25.5k+. Great!
LikeLike
There is always a danger to do with inequality, as it can lock in prejudice against a minority.
Maybe a flat tax has to be just that – from the first penny.
This is why i tend to feel consumption taxes have an advantage, in that they do operate equally for each penny spent by rich and poor alike and allows one to donate 100% of the monies one wants to donate without going cap-in-hand to ask for some of it back.
LikeLike