S. 147 : Reassessment-After the expiry of four years-Depreciation-Rate of depreciation-Computer software-Where depreciation on computer software was allowed at 60 per cent in the original scrutiny assessment, reopening the assessment after four years to restrict the rate to 25 per cent was held invalid as it was based on a mere change of opinion, there being no failure on the part of the assessee to disclose material facts. [S. 143(3), 148, Art. 226]