S. 263 : Commissioner-Revision of orders prejudicial to revenue-Lack of proper enquiry-Capital loss-Acquisition cost-Revision is up held-Bad debt-Revision is not valid-Depreciation of investment-Revision is valid-Bad debt-Provision for bad and doubtful debt-Revision is valid. [S.28(i) 36(1)(vii) 36(1)(viia), 45, 48, 70 143(3)]