Duty recovery and penalties: voluntary payment with interest and a fixed penalty enables conclusive proceedings if fully paid within the notice period. Amendment inserts subsection (1A) in section 28 allowing a person served with notice to pay duty in full or part, with interest under section 28AB and a penalty equal to twenty-five percent of the duty specified or accepted, within thirty days; added provisos to subsection (2) deem proceedings conclusive where full payment with interest and penalty is made, and allow the proper officer to determine remaining duty or interest where only part payment is made.