Unemp. Ins. Code, § 1224

(a) The petitioner or the director may, within 30 days after the service of notice of an administrative law judge’s decision under this article, file an appeal to the appeals board. The appeals board may for good cause extend the appeal period. If the administrative law judge fails to serve notice of the decision on a petition for review of denial of a claim for refund or credit within 60 days after a petition is filed, the petitioner may consider the petition denied and file an appeal with the appeals board. If an appeal is not filed within the 30-day period or within the additional period granted by the appeals board:

(1) The decision of the administrative law judge upon the petition is final in every case at the expiration of the period.

(2) Any assessment involved is final at the expiration of the period except that in cases where a decision of the administrative law judge requires an adjustment of an assessment by granting a portion of a petition or by increasing an assessment, the assessment is final 30 days after service upon the petitioner by the director of a statement of amounts due setting forth the adjusted liability pursuant to the decision.

(b) In the event of an appeal to the appeals board, it may decrease or increase the amount of any assessment involved. In cases where an order or decision of the appeals board requires an adjustment of an assessment by granting a portion of a petition or by increasing an assessment, the order or decision and the assessment become final 30 days after service upon the petitioner by the director of a statement of amounts due setting forth the adjusted liability pursuant to the order or decision of the appeals board. In all other cases, the order or decision of the appeals board and any assessment become final 30 days after service upon the petitioner of notice of the order or decision.