Hello, I am Keith, one of the experts on Just Answer, and pleased to be able to help you with your question.
The new rules are as follows and come in over a number of years, 2017 - 2021. Effectively they reduce landlord's tax relief to the basic rate of taxation only.
Here is an extract from the Gov UK web site:
'Landlords will no longer be able to deduct all of their finance costs from their property income to arrive at their property profits. They will instead receive a basic rate reduction from their income tax liability for their finance costs.
Landlords will be able to obtain relief as follows:
I do hope that my reply has been of assistance.