California Code, Revenue and Taxation Code - RTC § 212

(a) Notes, debentures, shares of capital stock, solvent credits, bonds, deeds of trust, mortgages, and any interest in that property are exempt from taxation.

(b) Money kept on hand to be used in the ordinary and regular course of a trade, profession, or business is exempt from taxation.

(c) Intangible assets and rights are exempt from taxation and, except as otherwise provided in the following sentence, the value of intangible assets and rights shall not enhance or be reflected in the value of taxable property.  Taxable property may be assessed and valued by assuming the presence of intangible assets or rights necessary to put the taxable property to beneficial or productive use.