Reasonable opportunity to be heard required - ensure penalty register maintenance and re-hearing before levying penalties. Failure to afford a reasonable opportunity of being heard in penalty proceedings led to appellate reversals where officers finalised orders after late service of notices or without re-hearing. Officers must maintain the prescribed penalty register, enter cases promptly after assessment, watch progress, and grant adjournments or re-notify as needed to comply with procedural requirements and prevent loss of cases on appeal.