S. 263 : Commissioner – Revision of orders prejudicial to revenue – Reassessment- Merger – Since the second round of reassessment proceedings were on the same set of facts as the first round, the same were dropped by the AO and thus the first reassessment order stood merged with the second.- Thus, the said order cannot be revised under Section 263 of the Act since only the valid reassessment order can be revised. [S.143(1), 147, 148]