Any deposit taken for a rental property on an AST must be put in a government approved tenant deposit scheme (TDS). The landlord must then provide the tenant and the person who paid the deposit (if different from the tenant) the prescribed information relating to the deposit and how it is held. Any private rental property in England must have the deposit registered with one of the following:
If you or your appointed agent fail to register the deposit within thirty days of receipt, you may be found liable for up to three times the deposit amount.
A landlord will not be able to enforce the use of a Section 21 of the Housing Act 1988 where a tenant’s deposit has not been protected with one of the government approved deposit protection schemes. More information about this can be found on GOV.UK - Deposit protection schemes and landlords.