Cal. Code Regs. tit. 18, § 13411 – Contingent or Conditional Transfer.

(a) If a taxable transfer is made subject to a contingency or condition upon the occurrence of which the interest of any transferee in the property involved may, in whole or in part, be created, defeated, extended, or abridged, the tax is computed at the highest rate possible upon the happening of the contingency or condition. For example, A by will transfers to B a life interest in property valued at $100,000, and to C, D, and E, or the survivor, a remainder interest in the property at B's death. C is not related to A. D and E are brothers of A. In such case the tax on the remainder will be compute on the supposition that the property will go to C, since a tax on a remainder to C would be computed at higher rates than on a remainder going to D or E (see Revenue and Taxation Code Sections 13404 through 13406 and 13307 through 13309). Any person who pays the tax so computed may secure a refund in the event that D or E survives B's death, in an amount equal to the difference between the tax paid and the tax which would have been payable had it been computed on the basis of a transfer to the actual survivor or survivors (see Revenue and Taxation Code Section 13956(b)).
(b) The payment of a tax due on a contingent or conditional transfer may be deferred on the filing of a bond (see Revenue and Taxation Code Sections 14171 through 14178), and may under proper circumstances be the subject of a compromise (see Revenue and Taxation Code Sections 14191 and 14192).
Note: Reference: Section 13411, Revenue and Taxation Code.