GST enforcement: summons/searches are investigative; show cause notices mark formal proceedings and define subject matter.
Issuance of summons, searches and seizures are investigative steps and do not constitute initiation of proceedings; formal adjudicatory commencement is principally the issuance of a show cause notice which defines the subject matter. The subject matter is determined from the show cause notice, and a twofold test-identity of liability on the same facts and identity or overlap of relief sought-governs whether two proceedings are the same. Cross-empowerment permits intelligence-based action by either authority, but parallel adjudications on identical subject matter are barred; authorities must coordinate and share information.