Landlord Mortage tax relief Back claim

Hi, I have a property which i have rented out since 2018. I have just realised I have not been claiming landlords mortgage tax relief. I am currently completing the self assessment for 2023-24. How many years can I back claim? Do I claim previous years in Box 45? Many Thanks

Hi,
You can only claim a tax refund up to 4 years after the end of the tax year it relates to, as we are in the 2024 to 2025 tax year the earliest tax year you can make a claim is for 2020 to 2021.
Please see:
Self Assessment tax returnsfor how you should make a claim.  
More information about the relief can be found in:
Tax relief for residential landlords: how it's worked out and the UK property notes SA105 for each year: UK property notes (2021) advise which box the relief can be claimed.
Thankyou