Tenancy agreement

Tenancy Deposits

Can I charge an admin fee to set up a tenancy without falling foul of them thinking they have paid a deposit ? I have a clause in the tenancy agreement 'An administration fee of £200 must be paid to enter into this tenancy'

If there is no admin fee or deposit what clause do I need to include.

The problem arises with tenants on benefits - we take 4 weeks rent off them in advance because they get their benfits payments 4 weeks in arrears so when they pay their benefits to us they also think they have paid a deposit - even though they are giving the benefits money to us in arrears !

Thank you