Cal. Code Regs. tit. 18 § 13951
The value of each item of property included in any transfer subject to the Inheritance Tax Law is ordinarily the market value of the property on the date of the transferor's death. "Market value," as a general rule, is the price that a willing buyer would pay to a willing seller of property, neither being under any compulsion to buy or sell.
If there is more than one unit of property included in a transfer, the market value of the whole will be determined by ascertaining the market value on the date of the transferor's death of each individual unit. In the case of a gift of stocks or bonds, each stock or bond will be treated as an individual unit.
All relevant facts and elements of value as of the date of the transferor's death will be considered in the determination of value. Depreciation or appreciation in value subsequent to the date of death are not relevant factors and will not be considered.
NOTE: Reference: Section 13951, Revenue and Taxation Code.
Cal. Code Regs. Tit. 18, § 13951