Mandatory filing duties and updated return limits reshape corrective filing eligibility and compliance obligations.
Section 263 imposes mandatory filing duties for enumerated classes, prescribes due dates by category, empowers the Board to prescribe forms and particulars, and allows the Central Government to exempt classes. It distinguishes late returns, revised returns (both within nine months or before assessment completion), and an updated return remedy within a multi year window that is barred where updated filings would claim losses, reduce tax, produce refunds, duplicate updates, or where assessments, possession of information, international or internal information exchange, prosecutions, searches, surveys, requisitions or specified notices have intervened. Assessing Officers may treat unrectified defective returns as invalid after a short cure period.