Retrospective amendment to section 10AA redefines profit attribution for SEZ units by substituting 'assessee' with 'undertaking'. The amendment substitutes the reference to assessee with undertaking in the apportionment rule under sub section (7) of section 10AA, preserving the export turnover based profit attribution while changing the statutory reference point for taxation. A proviso makes this substitution effective retrospectively to specified earlier assessment years and declares the retrospective operative date.