Interest on unpaid accumulations of lines after notice of demand.

(1) If an employer does not pay to the Board any amount of unpaid accumulations, or fines realized from the employees, within the time specified therefore by or under this Act, the Welfare Commissioner may serve or cause to be served a notice on such employer to pay the amount within the period specified therein which shall not be less than thirty days from the date of service of such notice. (2) If the employer fails, without sufficient cause, to pay any such amount within the period specified in the notice, he shall, in addition to the amount, pay by way of penalty to the Board simple interest- (a) for the first three month, at one per centum of the said amount for each complete month or part thereof after the last date by which he should have paid it according to the notice , and (b) for each complete month or part thereof thereafter, at one and half percentum of that amount during the time he continues to make default in the payment of that amount.