You will need to submit a separate claim for the earlier years and state the amounts you are claiming - please note the splits as per:-
Tax relief for residential landlords: how it's worked out
, you will also need to confirm that you are making a claim to overpayment relief.
All claims must be in writing to us at:
HM Revenue and Customs,
tell us you are claiming overpayment relief, give full details of the claim including
the amount of tax you have overpaid
why you have paid too much tax
the tax year / accounting period
if you have already appealed the calculation
if you are claiming repayment
any supporting documents showing tax paid
be signed by the customer - even if sent by an agent
confirm the details given are 'correct and complete to the best of my knowledge and belief'
The earliest year you can now apply for is 2019/20