S. 148A: Reassessment-Conducting inquiry, providing opportunity before issue of notice-Deceased person Details available on Income-tax portal-Notice invalid-Sanction-Mechanical sanction-Time limit wrongly mentioned as more than three years-Principal Commissioner had no power to approve-Approval sanction invalid. [S. 147, 147, 148A(b) 148A(d) 151, Art. 226]