Cal. Probate Code § 6409

(a) If a person dies intestate as to all or part of his or her estate, property the decedent gave during lifetime to an heir is treated as an advancement against that heir’s share of the intestate estate only if one of the following conditions is satisfied: (1) The decedent declares in a contemporaneous writing that the gift is an advancement against the heir’s share of the estate or that its value is to be deducted from the value of the heir’s share of the estate. (2) The heir acknowledges in writing that the gift is to be so deducted or is an advancement or that its value is to be deducted from the value of the heir’s share of the estate. (b) Subject to subdivision (c), the property advanced is to be valued as of the time the heir came into possession or enjoyment of the property or as of the time of death of the decedent, whichever occurs first. (c) If the value of the property advanced is expressed in the contemporaneous writing of the decedent, or in an acknowledgment of the heir made contemporaneously with the advancement, that value is conclusive in the division and distribution of the intestate estate. (d) If the recipient of the property advanced fails to survive the decedent, the property is not taken into account in computing the intestate share to be received by the recipient’s issue unless the declaration or acknowledgment provides otherwise.