Penalty imposition power when no parallel GST proceeding exists, subject to reasonable opportunity to be heard. Section 127 authorises the Proper Officer to levy a penalty when liability is found and the matter is not covered by specified GST proceedings-such as assessments of non filers, assessments of unregistered persons, summary assessments, demands for non payment or short payment or erroneous refund, determinations of tax not paid or wrongly availed input tax credit for later years, or detention, seizure or confiscation proceedings-and only after the person is given a reasonable opportunity of being heard.