Return filing due dates and revised return rules under section 139 are restructured with updated return exceptions and notice-based filing limits. Amendment of section 139 revises the due dates for returns under sub-section (1), permits revised returns where omissions or statements are discovered, and modifies the updated return regime under sub-section (8A). The substituted Explanation 2 prescribes different due dates based on assessee category, audit status, and applicability of section 92E. Revised returns may be filed subject to section 234-I before the end of the relevant assessment year or completion of assessment, whichever is earlier. Updated returns are further adjusted for loss-reduction cases and for returns furnished in response to a notice under section 148.