(1) If an employer fails to file reports for the purpose of determining the amount of contribution in accordance with the regulations of the commissioner, or files manifestly incorrect or insufficient reports, the commissioner may assess the contribution and any interest due on the basis of the information submitted by the employer or on the basis of an estimate as to the amount due and shall give written notice of such assessment to such employer: Provided, That such assessment shall be subject to redetermination by the commissioner upon the filing by the employer of correct and sufficient reports within thirty days after notice of such assessment shall be given to him
