Cal. Code of Civil Procedure § 2030.290

If a party to whom interrogatories are directed fails to serve a timely response, the following rules apply: (a) The party to whom the interrogatories are directed waives any right to exercise the option to produce writings under Section 2030.230, as well as any objection to the interrogatories, including one based on privilege or on the protection for work product under Chapter 4 (commencing with Section 2018.010). The court, on motion, may relieve that party from this waiver on its determination that both of the following conditions are satisfied: (1) The party has subsequently served a response that is in substantial compliance with Sections 2030.210, 2030.220, 2030.230, and 2030.240. (2) The party’s failure to serve a timely response was the result of mistake, inadvertence, or excusable neglect. (b) The party propounding the interrogatories may move for an order compelling response to the interrogatories. (c) The court shall impose a monetary sanction under Chapter 7 (commencing with Section 2023.010) against any party, person, or attorney who unsuccessfully makes or opposes a motion to compel a response to interrogatories, unless it finds that the one subject to the sanction acted with substantial justification or that other circumstances make the imposition of the sanction unjust. If a party then fails to obey an order compelling answers, the court may make those orders that are just, including the imposition of an issue sanction, an evidence sanction, or a terminating sanction under Chapter 7 (commencing with Section 2023.010). In lieu of or in addition to that sanction, the court may impose a monetary sanction under Chapter 7 (commencing with Section 2023.010).