If a company was a tenant in a residential assured shorthold tenancies (potentially on the behalf of employees without using a service occupancy agreement) what may be the legal ramifications?

Under section 1 of the Housing Act 1988 (HA 1988), only an individual(s) can hold an assured tenancy (AT) and accordingly an assured shorthold tenancy (AST). Therefore, a company cannot hold an AST. See Commentary: Letting must be to an individual who has his main home in the dwelling-house: Claims to the Possession of Land [C3.5].

It is also unlikely that the tenant company holds a business tenancy under the Landlord and Tenant Act 1954 (LTA 1954) on the basis that it is unlikely the tenancy falls within the definition under LTA 1954, s 23, ie a tenancy is within LTA 1954 if the whole or a part of the demised premises is occupied by the tenant for the purposes of its business or for those and other purposes. The expression 'business' includes any trade, profession or employment. It also includes any activity carried on by a body of persons, whether corporate