Discretion to reduce or waive penalties: relief available for voluntary disclosure, cooperation and satisfactory payment arrangements. Section 273A empowers the Commissioner or Principal Commissioner to reduce or waive penalties, stay or compound recovery, subject to conditions: voluntary and bona fide prior disclosure, cooperation in inquiries, and payment or satisfactory arrangements for tax or interest; supervisory approvals are required in specified serious cases, applications must be decided with reasons and within prescribed time-frames, and every order under the section is final.