Who decides?
It is a matter for the authority to determine who is and who is not a tenant. You might think it wise to refer the following to your legal department for an opinion as to whether or not they are "tenants":

Service occupants; "Rental Purchasers"; People who do not pay rent in money; Beneficial life tenants.

Landlord applications

The Rent Officer will decide what type of tenancy exists as a preliminary to setting a market rent. He may or may not tell you his conclusions. If he does, you must still decide yourself lest you fetter your discretion by improper delegation. You may of course take his advice into account.

Vine v National Dock Labour Board [1957] AC 488 Ellis v Dubowski [1921] 3 KB 621 Mills v LCC [1925] 1 KB 213 R v GLC ex parte Blackburn [1976] 1 WLR 550