No portion of a security deposit is non-refundable.
Tenants can protect themselves from unjustified deductions at the end of a tenancy.
First, they should clean the unit after they move their belongings. The apartment should be restored to the condition it was in at the beginning of the tenancy. Second, tenants should document the condition of the apartment when they move. For example, they can take photos of every room, have a friend inspect the apartment, or arrange a walk through inspection with the landlord. Third, tenants should give the landlord their forwarding address.