Thank you for reply.
The deposit has sort of rolled, and was initially taken about 18:years ago and I have not tried to do anything wrong.
Had a tenant who paid the deposit, (18 years ago) , she moved out and her sister took the property (12 years ago) then in April 2020 ( full COVID lockdown) the original sister moved back in. So the deposit money just rolled as I have never kept any back.
I have never had to ask anyone to leave, hence unsure of the wording for the letter.