Show Cause Notice practice: officers may issue SCNs for customs duty and interest within prescribed statutory timeframes. The procedure bars serving a demand notice for amounts below the de minimis threshold in Section 28(1)(b). Show cause notices for duty or interest under Sections 28, 28AA and 28AAA may be issued by the proper officer or by an officer subordinate to the proper officer under Section 5(2), and must be issued within the prescribed statutory time limits or any permitted extension.