Sorry if this has been discussed previously but search is not bringing back the answers specific to my situation

I am a British Citizen and my wife is applying for ILR Set (M). So far we have submitted the application and in the process of uploading the docs from the checklist on third party website who are doing the interview.
In the checklist it states the following:
Letter signed by the owner of the property you live in stating that you have permission to live thereI am currently the owner of the house i.e. mortgaged to me so it makes me the landlord. So how do I prepare the letter in this situation? Do I really need to prepare a letter for this? I have read somewhere I can send the Land registry in this case?
Is this true? Can somebody please guide me for this?