Each license required by this chapter shall be renewed annually, on or before the first day of the first month of the licensee’s license year, by application to the director, accompanied by the annual license fee. An application and annual license fee sent by mail is not overdue if postmarked not later than the fifth day of the month in which it is due. To any fee not paid when due, there shall be added a penalty equal to 30 percent of the amount of the license fee, if it is paid within 30 days of becoming due. The penalty for a renewal fee more than 30 days after becoming due shall be 100 percent of the amount of the license fee. However, no penalty shall be applicable to the renewal of deputy weighmaster licenses.