Search-triggered assessment extends retrospective reassessment scope and prescribes a specialized time-bar and procedural rules for affected taxpayers. Sections 153A-153C establish a special assessment procedure following a search under section 132 or requisition under section 132A: the Assessing Officer may require returns and assess or reassess total income for the preceding assessment years under the Act, with pending assessments within that period abating. A tailored time-limit requires completion of such assessments within a specified period from the end of the financial year in which the final search or requisition authorisation was executed, subject to enumerated exclusions and a minimum residual-period extension. Deemed execution rules and transfer of seized or requisitioned material to the proper Assessing Officer for other persons are provided.