Consequences of failure to pay duty beyond 30 days [Sub-rule (3A)]:

If the assessee fails to pay the duty declared as payable by him in the return within a period of 1 month from the due date, then he would be liable to pay penalty @ 1% on such amount of the duty not paid, for each month or part thereof calculated from the due date, for the period during which such failure continues. Here, “month” means the period between two consecutive due dates for payment of duty