(a)an order passed ] [Substituted by Act 26 of 1988, Section 57, for Explanation (w.e.f. 1.6.1988). ] [on or before or after the 1st day of June 1988,] [Inserted by Act 13 of 1989, Section 30 (w.r.e.f. 1.6.1988). ][by the Assessing Officer shall include an order made by the Joint Commissioner in exercise of the powers or in the performance of the functions of an Assessing Officer conferred on or assigned to him under orders or directions issued by the Board or by the Chief Commissioner or Director General or Commissioner authorised by the Board in this behalf under section 120 of the Income-tax Act read with section 8 of this Act;