Block assessment procedure: notice requires furnishing of return treated as regular return; AO determines undisclosed income and assesses tax. Where a search under section 132 or requisition under section 132A occurs on or after 1 September 2024, the Assessing Officer, after specified senior approval, shall issue a notice requiring the person to furnish within the notice period a prescribed return setting forth the undisclosed income for the block period; such return is treated as a return under section 139 (except when filed beyond the allowed period), no revised return is permitted, no section 148 notice is required, the AO shall determine the total undisclosed income per section 158BB applying specified procedural provisions and shall pass an assessment or reassessment, and seized or requisitioned assets shall be dealt with under the seized-assets framework.