S. 151 : Reassessment-Sanction for issue of notice-After the expiry of four years-Corporate social responsibility-Sanction of Commissioner or Principal Commissioner is a pre-requisite for issuance of a reopening notice under section 148 after expiry of four years from end of relevant assessment year-Reopening notice with sanction of Additional Commissioner was quashed and set aside. [S. 35AC, 80G, 92CA, 147, 148, 151(2), Art. 226]