Paying a Deposit
If you signed a tenancy agreement for an assured shorthold tenancy and paid a deposit on or after 6th April 2007 your deposit will be covered by the Tenancy Deposit Scheme.
The landlord or Lettings agent must put your tenants’ deposit in the scheme within 30 days of getting it.
If your tenancy is covered by the scheme and the landlord has not complied with the rules, you can enforce your rights under the Housing Act 2004 by applying to the County Court.
For more guidance you can check out: england.shelter.org.uk/housing_advice/tenancy_deposits