Ans: It is an identification number generated when you register on the Income Tax web portal. It stands for the Income Tax Department Reporting Entity Identification Number. Once this number is generated, it remains active. Income Tax Department uses this number as an identification number for you. You need to use this number for all the future Income Tax filings. Individuals on their own can not deactivate this number. It follows following 16 number format, *********** YZNNN The decoding of the components of the ITDREIN is as follows:  *  represents your PAN or TAN number Y represents your form code Z represents your category of reporting entity  N represents the sequence number of the Code