Held that every income tax authority shall allot a new computer generated Document Identification Number (DIN) in respect of every communication by way of notice, order, letter or any correspondence issued by him to any other income tax authority or assessee or any other person and such number should be quoted thereon. Any such order, notice, correspondence etc. which does not bear DIN in body of communication shall be treated as invalid in eyes of law and shall be deemed to have never been received. Where approval granted under section 153D by Additional Commissioner to draft assessment order was without issuance of DIN, final assessment order so passed under section 153A on basis of such invalid and non-est approval under section 153D is  without sanction of law and  invalid. (AY. 2017-18)