Every person (being an Individual or HUF, whether Resident or Non-resident) whose Total annual Income exceeds the basic exemption limit (Rs.5,00,000 for Super-senior individuals, Rs.3,00,000 in case of Senior individuals & Rs.2,50,000 for the rest) shall have to compulsorily file Income Tax Return. Further, every Company and Firm are compulsorily required to file their Income Tax Return (irrespective of whether they are having any income or loss).
E-filing of ITR has been made mandatory for a) Companies (whether Private Limited or Public Limited), b) Partnership Firms, c) Limited Liability Partnerships (LLP), d) category of taxpayers to whom ITR form nos. 3 & 4 are applicable, e) an individual who want to claim any amount of Refund, f) individual taxpayers whose Total annual income exceeds Rs.5,00,000, g) an individual who is a resident of India and has assets (including financial interest in an entity) located outside India, h) an individual who is a resident of India and is a signing authority in any bank account located outside India, and i) an individual who is a resident of India and has income from any source outside India.
Non filing of Income Tax return after end of a specified period attracts a penalty Rs. 5,000 along with penal interest under section 234A of The Income Tax Act. Further, some 'losses' sustained during a financial year cannot be carried forward to subsequent year if your ITR is not filed or is filed after the due date.
The last date filing ITR is a) July 31 in case of Individuals, HUF's, Non-working Partners in a Partnership firm & taxpayers not covered by Tax Audit provisions, and b) September 30 in case of Companies, Working Partners in a Partnership firm and taxpayers covered by Tax Audit provisions.