S. 263: Commissioner-Revision of orders prejudicial to revenue–Notice and order issued in name of erstwhile company but mentioning factum of amalgamation in cause title-Not invalid-Nothing to establish that issues on which revision exercised were examined by Assessing Officer during assessment-Duty cast on Assessing Officer to examine issues not performed-Order of Principal Commissioner setting aside assessment order-Proper. [S. 14A, 40(a)(i), 143(3)]