Provisional assessment time limits for customs duty clarified; finalisation required within prescribed period with allowed extensions and exceptions. Amendments require the proper officer to provisionally assess duty and to finalise such provisional assessments within two years, with a possible one year extension by the Principal Commissioner or Commissioner for sufficient cause; pending assessments on enactment are reckoned from presidential assent. Specified grounds-foreign information requests by legal process, pending appeals or stays, Board directions, and pending Settlement Commission or Interim Board applications-allow suspension of the finalisation period, provided the proper officer informs the importer or exporter and the two year period then runs from cessation of the reason for delay.