As mentioned in clause (a) of Explanation 2 to subsection 1 of Sec. 139, following assesses are required to file their Income Tax Return by 31^st October of the assessment year:

1. A company;
2. A person (other than a company) whose accounts are required to be audited under this Act or under any other law for the time being in force;
3. A partner of a firm whose accounts are required to be audited under this Act or under any other law for the time being in force [or the spouse of such partner if the provisions of section 5A applies to such spouse]