Assigning a unit means that the tenant moves out of the unit permanently and transfers their tenancy to another person. Subletting a unit means that the tenant moves out of the unit for a period of time but plans to move back in before the end of the tenancy. A tenant must have the landlord's approval to assign or sublet the unit, but the landlord must have a good reason to refuse. Refer to the Ontario Landlord & Tenant Board for detailed information.