S. 254(1): Appellate Tribunal-Powers-Additional grounds-Challenge to validity of reassessment raised before Commissioner (Appeals) and rejected-Assessee in Department’s appeal filing application raising ground relating to validity of assessment-Tribunal justified in accepting ground and holding reassessment was on change of opinion and unsustainable in law.[S. 147, 148, (Appellate Tribunal) Rules, 1963, R. 27.]