Retrieving Log in credentials

Suvabrata Roy (Lawyer) (62 Points)

06 August 2017  
The application for registration was approved by the department and the log in credentials were mailed to the registered mail lD of my client who had inadvertently deleted the mail from his inbox. Now how to retrieve the log in credentials as he only has the GSTIN number with him which is of no use for generating a new user ID.
Friends please help.
Thanking all of you in advance.