Tenancy deposits are normally returned in their entirety at the end of a tenancy. In the event the tenant has caused damages to the property then the landlord can use the deposit to fund repairs. Similarly, if the tenant has unpaid rent or the landlord has suffered any other loss caused by the tenant then up to 100% of the deposit can be withheld.
The landlord must supply their reasons and estimations in writing for any deductions to the deposit. Since 2007, the deposit must be placed in a Protected Scheme for the entirety of the tenancy.