Speaking as a pedant: The top marginal rate is actually 60% and happens when you cross the threshold where you're nominally in the 40% band but you're also losing your personal allowance. The effect is, for every £2 extra income you lose £1 personal allowance (exposing an extra £1 to taxation) and pay 40p tax on that. That's 20% in addition to the 40% you're paying anyway, hence 60% marginal rate. Once you hit the income level where all your personal allowance has been fully cancelled out, then your marginal rate drops back down. And then the next threshold after that puts you in the 45% band.