If in the opinion of the commission the return of any employer is incorrect, the commission may revise such return and may audit and state an account according to such revised return for the amount due from such employer for the assessment, penalties and interest. If an employer fails to make a return, the commission may estimate his gross payroll payments from any information available to it. For this purpose, the commission may examine the employer's books and records, take testimony, require other evidence, and audit and state an account according to such information of the amount due from the employer for the assessment, penalties and interest. Nothing in this section is intended to or shall be construed to limit the investigating or auditing powers of the commission under the Act.