1. He do not remember the Email ID on which he registered
2. He forget the password of registered email id
3. Registered email id belongs to someone else i.e employee of the taxpayer, Consultant etc. and he is not aware who this email id belongs and even if he knows it is possible that they refuse to provide password sent by department.
In all the above cases taxpayer to login into his account on income tax portal taxpayer can request a new password by writing a email on the email id firstname.lastname@example.org mentioning his NAME, PAN & Registered Address with Income Tax Department. Once done with this, taxpayer will receive the password of the Income Tax e-filing account within 48 hours on new email ID.