Cal. Rev. & Tax. Code § 723

The board may use the principle of unit valuation in valuing properties of an assessee that are operated as a unit in a primary function of the assessee. When so valued, those properties are known as “unitary property.” Property of an assessee not valued through the use of the principle of unit valuation are known as “nonunitary property.” When valuing nonunitary property, the board shall consider current market value information of comparable properties provided by the assessor just prior to the reappraisal by the board of that property.