It is not uncommon for a landlord and a tenant to sign a one-year lease for a rental property just to discover a couple months later, that the tenant has moved someone in. Is the additional occupant a tenant? The answer is…it depends.
If the terms of the lease expressly prohibit occupancy to an additional inhabitant without the landlord’s consent, then allowing someone to move in is a breach of the lease. Upon discovery of such, the landlord may start a for cause summary process action against both the tenant and the other occupant. If after learning of the new occupant, the landlord takes no action, this lease violation may be considered waived. The new occupant may continue to stay as an invitee of the first tenant.
On the other hand, if the landlord accepts some rent payments from the new occupant, a Tenancy At Will is created. The new occupant is now a tenant. A tenancy at will does not have to be in writing, it can be oral or even a mere understanding created by the conduct of the landlord and the new occupant. A tenancy at will lasts indefinitely; at the end of the one year lease, the tenancy with the first tenant automatically expires but the second tenant still has a tenancy at will with the right to remain in possession of the property until the landlord or the second tenant terminate the tenancy.
Whether the second occupant is an invitee or a tenant at will, removal from the premises still requires the landlord to go through the legal process.
Word of advice: Lease terms should contain clear, unambiguous language expressly prohibiting the tenant from allowing additional occupants to live on the premises. If the tenant violates the terms of the lease, take immediate action. Landlords have two options: start a summary process or offer to sign a new lease to include any additional occupants.