S. 263 : Commissioner-Revision of orders prejudicial to revenue-Depreciation-Lease of assets-Operating lease and finance lease transactions-lessee only had right to use vehicles-Entitle depreciation-Revision is not valid-Method of accounting-Estimate of income-Excess interest spread (EIS)-Revision is not valid-Chargeable in the year of receipt. [S. 2(28A), 32, 143, 145]