Income Tax Representative assessee

In order to register as a representative assessee on a behalf of deceased, you need to log in using deceased person account details not the representative account. Ensure that u have the necessary authority and relevant information for the registration process

First you must get approval from ITD by registering as a legal representative .. after their approval *viz*, Logon to the „e-Filing‟ websitewww.incometax.gov.in (Legalheir's Login credentials) > Dashboard >My Profile > Select the drop downunder “Logged in as” -Legal Heir > and follow the given steps to Go toe-File > Income Tax Return > File Income tax Returns.
this is a simply a few steps which I have done to file ITR for deceased family member.

As per the norms

In order to register as a representative assessee on a behalf of deceased, you need to log in using the  intended representative assessee's e-filing  account. You need to upload Deceased person's PAN CARD, Death Certificate ad legal heir certificate.