Backdating Mortgage interest to gain 20% relief

I, incorrectly, thought I was not able to claim anything on the mortgage interest and therefore have not entered the value of my mortgage interest into box 26 on the last couple of years, since the changes to mortgage interest relief. Is it now possible to backdate claims for basic 20% tax relief on rental property mortgage interest, and if so for how many years and how do I enter it on tax form?

Hi,

You can go back four years to make a claim for tax relief not given by making an overpayment relief claim. You can see more details here:

SACM12150 - Overpayment relief: Form of claims

Thank you.