Contributions shall accrue and become payable by each employer for each calendar year in which he is subject to Chapters 27 through 41 of this Title with respect to wages for employment. Such contributions shall become due and be paid by each employer to the Commission for the fund in accordance with such regulations as the Commission may prescribe and shall not be deducted, in whole or in part, from the wages of individuals in such employer's employ. Provided, however, no determination and assessment of contributions, interest, or penalties shall be made, and no action for the collection of contributions, interest, and penalties shall be instituted more than four years after the last day of the month immediately following the calendar quarter for which such contributions, interest or penalties were payable. Provided, further, that this proviso shall not apply to any employer if the Commission finds that the employer willfully failed to report, when required to do so by the provisions of this law or the rules and regulations of the Commission, or has knowingly made a false statement or has intentionally failed to disclose a material fact.