Excess duty liability broadened: duty liable collectors face show cause, assessment adjustment and refund procedures. The amendment broadens section 11D liability to persons liable to pay duty who collect amounts in excess of assessed duty, and replaces prior subsections with a procedure whereby a Central Excise Officer issues a show cause notice, determines the amount due after representations, requires payment, permits adjustment of amounts against final assessment, and directs surplus crediting or refund under section 11B with a time limited application following public notice.