Held that an assessment order passed by Assessing Officer without obtaining Document Identification Number (DIN) is invalid and shall be deemed to have been never passed. Where Assessing Officer passed an assessment order under section 143(3) without issuing notice under section 143(2) only in pursuance with notice issued by another Assessing Officer under section 143(2), who had no jurisdiction over assessee at relevant time, such assessment order was liable to be quashed as no valid notice under section 143(2) was issued by Assessing Officer who held jurisdiction over case of assessee. (AY. 2014-15, 2017-18)