5. This Part also applies in a case where a rent officer has made a determination in respect of a tenancy of a dwelling and by virtue of paragraph 2 of Schedule 1A to the Housing Benefit Regulations(1) (cases with existing determinations) a new determination is not required in respect of another tenancy of the dwelling and in such a case the determination made shall, for the purposes of this Part, be treated as if it were a determination made in respect of that tenancy.