97.(1) The Commission shall fix the percentage, rate or sum for which each employer is assessed under the provisions of sections 95 and 96, or the provisional amount thereof, and such employer shall pay to the Commission the amount or provisional amount of his assessment within one month, or such other time as the Commission may fix, to run from the notice of the assessment and of the amount to be paid. Where payment is to be made by instalments, the employer shall pay the first instalment within the above-mentioned delay, and the remaining instalment or instalments at the time or times specified in such notice.
(2) The notice may be sent by post to the employer and shall be deemed to have been given to him on the day on which the notice was posted.
(3) Wherever it appears that a statement or estimate of pay-roll, upon which an assessment or provisional amount of assessment is based, is too low, the employer shall upon demand pay to the Commission such additional sum, to be fixed by the Commission, as will bring the payment of assessment or provisional amount up to the proper amount; and the employer may be compelled to the payment of any such sum in the same manner as the payment of any assessment may be enforced.