S. 263 : Commissioner-Revision of orders prejudicial to revenue-Jurisdiction to be tested with reference to law prevailing on date of exercise of revisional power-Subsequent Supreme Court decision cannot invalidate revision-Lack of enquiry by Assessing Officer on section 32AB deduction and computation of book profits under section 115J rendered assessment erroneous and prejudicial-Commissioner’s order to be read as a whole and not by isolating one sentence-Where assessee did not challenge order giving effect to section 263, merits could not thereafter be agitated-Tribunal upholding assumption of jurisdiction affirmed. [S. 32AB, 115J, 260A]