California Code, Revenue and Taxation Code - RTC § 24911

(a) The adjusted basis for determining the gain or loss from the sale or other disposition of property, whenever acquired, shall be the basis (determined under Section 24912) or other applicable sections of Chapter 15  1 (relating to gain or loss on disposition of property) and Chapter 8  2 (relating to corporate distributions and adjustments), adjusted as provided in Sections 24916 and 24917.

(b) If a deduction is allowable under Section 24357 (relating to charitable contributions) by reason of a sale, then the adjusted basis for determining the gain from such sale shall be that portion of the adjusted basis which bears the same ratio to the adjusted basis as the amount realized bears to the fair market value of the property.