The deposit is the tenants money and you need to take steps to ensure it is returned when you move out.

Understanding your obligations as a tenant and having an inventory of contents at the beginning of the tenancy will greatly help to reduce the chances of a dispute arising over the return of your deposit. However if you feel the deductions are unjustified the first step is to discuss the matter with your landlord or agent and to try to come to an amicable solution. If you are unable to come to an agreement you are entitled to take a case to the PRTB (Private Residential Tenancies Board).