Assessing Officer initially passed an assessment order under section 143(3) on 15-9-2021, determining total income.Subsequently, a draft assessment order was passed under section 144C(1) on 30-9-2021, with same income figure.Assessing Officer stated that order under section 143(3) was passed on 15-9-2021 inadvertently and therefore, said order might be read as draft order under section 144C. Dispute Resolution Panel (DRP) held that once final assessment order had been passed on 15-9-2021 under section 143(3), same could not be annulled or modified at a subsequent date on ground that same was passed inadvertently.However, instead of complying with DRP’s directions, Assessing Officer passed a final assessment order on 27-6-2022, replicating draft order. Tribunal held that once an assessment order has been passed under section 143(3) in respect of any assessment year, Assessing Officer cannot tinker with that assessment, of course, he can either reopen assessment or rectify assessment order after strictly complying with conditions of section 147 and respectively and statute does not confer any powers on Assessing Officer to either withdraw or modify or substitute assessment order passed under section 143(3) with another assessment order Therefore, final assessment order passed by Assessing Officer without complying with directions of DRP was without jurisdiction and deserved to be set aside and quashed. (AY. 2017-18)