Cal. Code Regs. tit. 18 § 15306
The usual presumption that property acquired by a husband or wife after marriage is community property does not apply as against any claim by the State for the gift tax. The burden of proving any property to be community property is on the person who claims that it has such status. A claim that property is community property must be supported by form GT-3, entitled "Marital Property Declaration." This declaration should be executed by one of the spouses, or if it is for some reason impossible for one of the spouses to execute the declaration, by any person having actual knowledge of the facts required, and submitted to the State Controller. Copies of form GT-3 may be obtained from the Division Tax Administration Gift Tax of the Controller's office in Los Angeles, Sacramento or San Francisco.
Cal. Code Regs. Tit. 18, § 15306
Note: Authority cited: Section 16506, Revenue and Taxation Code. Reference: Section 15306, Revenue and Taxation Code.