Where an order determining the amount due from an employer under section 7A or section 7B has been passed and if the officer who passed the order—

(a) has reason to believe that by reason of the omission or failure on the part of the employer to make any document or report available, or to disclose, fully and truly, all material facts necessary for determining the correct amount due from the employer, any amount so due from such employer for any period has escaped his notice;

(b) has, in consequence of information in his possession, reason to believe that any amount to be determined under section 7A or section 7B has escaped from his determination for any period notwithstanding that there has been no omission or failure as mentioned in clause (a) on the part of the employer,