Cal. Rev. & Tax. Code § 19354

If the amount allowable as a credit under Section 19002 (relating to credit for tax withheld) and the amount, if any, allowable as a refundable tax credit (including the Child and Dependent Care Credit allowable under Section 17052.6) exceeds the tax imposed by Part 10 (commencing with Section 17001), against which the credits are allowable, the amount of the excess shall be considered an overpayment.