When George Osborne was Chancellor of the Exchequer, he wanted to find ways of solving the housing shortage and get more people on the property ladder.
If you wanted to buy a home to live in, he reasoned, you faced unfair competition from buy-to-let landlords. Unlike them, you couldn’t (for tax purposes) offset your mortgage interest payments against income from the property.
So, in 2015, he decided to change the rules. A new act of parliament said that, from the tax year 2017-2018, the amount of ‘finance costs’ that landlords could claim against property income would begin to fall (if they paid higher or additional rate income tax).