California Code, Probate Code - PROB § 20120

(a) The personal representative or any person interested in the estate may commence a proceeding to have a court determine the proration pursuant to this chapter.

(b) A proceeding under this article shall be commenced in the court in which the estate of the decedent was administered or, if no administration proceedings have been commmenced,  1 in the superior court of any county in which the estate of the decedent may be administered.

(c) If proceedings for the administration of the decedent's estate are pending, a proceeding under this article shall be combined with the administration proceedings. If a proceeding is commenced at any time before final distribution, there shall be no additional filing fee.