If the director finds that an assessment or portion thereof has been erroneously made, he may cancel the assessment or portion thereof in the following cases:
(a) Where no petition for reassessment has been filed.
(b) Where a petition for reassessment is filed, if the cancellation is made prior to the mailing of a decision of the administrative law judge.
(c) Where a petition for reassessment has been filed and an order or decision of an administrative law judge
or of the appeals board has been issued on any grounds not on the merits, if the cancellation is approved by the appeals board.