155. (1) The Appellate Joint Commissioner ²[or the Commissioner (Appeals)] shall fix a day and place for the hearing of the appeal and give notice thereof to the appellant and the Deputy Commissioner of Taxes against whose order the appeal has been preferred. (2) The appellant and the Deputy Commissioner of Taxes shall have the right to be heard at the hearing of the appeal either in person or by a representative. (3) The Appellate Joint Commissioner ³[or the Commissioner (Appeals)] may, if he considers it necessary to do so, adjourn the hearing of the appeal from time to time. (4) The Appellate Joint Commissioner ⁴[or the Commissioner (Appeals)] may, before or at the hearing of an appeal, allow the appellant to go into any ground of appeal not earlier specified in the grounds of appeal already filed if he is satisfied that the commission of that ground from the form of appeal was not wilful or unreasonable. (5) The Appellate Joint Commissioner ⁵[or the Commissioner (Appeals)] may, before or at the hearing of an appeal, make such enquiry as he thinks fit or call for such particulars as he may require respecting the matters arising in appeals or cause further enquiry to be made by the Deputy Commissioner of Taxes. (6) While hearing an appeal the Appellate Joint Commissioner ⁶[or the Commissioner (Appeals)] shall not admit any documentary material or evidence which was not produced before the Deputy Commissioner of Taxes unless he is satisfied that the appellant was prevented by sufficient cause from producing such material or evidence before the Deputy Commissioner of Taxes.