Computation of undisclosed income: block-period undisclosed income aggregated from declared returns and AO determinations, excluding international transaction income. Total undisclosed income of a block period equals undisclosed income declared in the special return plus undisclosed income determined by the Assessing Officer. Certain incomes are excluded, notably amounts assessed or declared before initiation of search or requisition and incomes computed from books maintained in the normal course for specified sub-periods; the Assessing Officer may recompute any part he considers undisclosed. Evidence from search, survey, requisition or other material available to the Assessing Officer forms the basis for determination, while income from international or specified domestic transactions for the terminal period is excluded from block-period computation and assessed separately.