Provisional and re assessment of customs duty: officers may direct provisional assessment subject to security when further enquiry or testing is needed. The amendment allows a proper officer to direct a provisional assessment of customs duty where self assessment is impracticable on written request, where goods require chemical or other tests, where further enquiry is necessary despite production of documents, or where documents/information are missing, subject to security for any deficiency; it also inserts and standardises references to re assessment throughout section 18 so duties and orders are described as 'finally assessed or re assessed, as the case may be.'