Central Board of Direct Taxes (CBDT) has issued a notification S.O. 626(E) dated 28th March 2012 vide which e-Filing has been made compulsory for Assessment Year 2012-13 onwards for an individual or a Hindu undivided family, if his or its total income, or the total income in respect of which he is or it is assessable under the Act during the previous year, exceeds ten lakh rupees; and an individual or a Hindu Undivided Family (HUF), being a resident, having assets (including financial interest in any entity) located outside India or signing authority in any account located outside India and required to furnish the return in Form ITR-2 or ITR-3 or ITR-4.
However, digital signature will not be mandatory for these taxpayers and they can also transmit the data in the return electronically and thereafter submit the verification of the return in Form ITR-V.
Filing of returns electronically under digital signatures is already mandatory for any company required to furnish the return in Form ITR-6 or a firm required to furnish the return in Form ITR-5 or an individual or HUF required to furnish the return in Form ITR-4 and to whom provisions of section 44AB are applicable. Source