Notice to show cause requires serving supporting information and allowing a reply before issuing a tax escape assessment notice. Where material suggests income has escaped assessment, the Assessing Officer must serve a notice to show cause accompanied by that information and allow the assessee a specified period to reply; after considering the record and any reply, the Assessing Officer, with prior approval of the specified authority, must determine whether the case is fit to issue a notice under section 280. The section excludes cases based on information under the scheme notified under section 260, directions of the Approving Panel under section 274(6), or findings or directions in orders of any authority, Tribunal, or court.