Abatement of assessments: assessments for block-period years abate on initiation of search or requisition, clarifying undisclosed income scope. The provision replaces 'total income' with 'total undisclosed income' across the section, introduces an abatement rule whereby assessments, reassessments and recomputations for block-period years abate on initiation of a search or requisition (and certain notices issued in the interval also abate), expands proceedings to include recomputation, reference and order, and substitutes language changing 'pending' to 'required to be made'.