Reopening of completed assessments permitted only through statutory reopening framework, subject to incriminating material and procedural conditions. Where incriminating material is found in a search or requisition, the AO may assess or reassess total income using that material and other records; where no incriminating material is found, additions cannot be made in completed/unabated assessments based solely on other material. Completed assessments may, however, be reopened under the statutory reopening framework subject to its conditions, procedural safeguards, sanction requirements, and applicable time limits. AOs must classify cases as abated or unabated, revive annulled proceedings where applicable, apply prescribed administrative timelines, and take appellate or remedial steps where later decisions conflict with the Apex Court's ratio.