Classes of officers under IGST define a multi-tier administrative hierarchy and permit appointment of additional officer classes as needed. The Act establishes a structured administrative hierarchy for IGST comprising successive tiers of officers-from Principal Chief Commissioners/Principal Directors General through Chief Commissioners/Directors General, Principal Commissioners/Principal Additional Directors General, Commissioners/Additional Directors General, Additional Commissioners/Additional Directors, Joint Commissioners/Joint Directors, Deputy Commissioners/Deputy Directors, and Assistant Commissioners/Assistant Directors-and permits appointment of such other classes of officers as may be required for the Act's purposes.