A dealer shall not be entitled to produce additional evidence whether oral or documentary in appeal before the Additional Commissioner or Appellate Deputy Commissioner or the Tribunal or in revision before the Commissioner except where the evidence sought to be adduced is evidence, which the assessing authority had wrongly refused to admit or which after exercise of due diligence was not within his knowledge or could not be produced by him before the assessing authority or for the production of which adequate time was not given by the assessing authority and in every such case upon the additional evidence being taken on record reasonable opportunity for challenge or rebuttal shall be given to the Commissioner.