Court held that the fact of discovery of the details from the premises of the assessee itself postulated a deliberate defiance in complying with the applicable provisions of law. However, penalty could only be with respect to that income, which was not disclosed in the returns or in the return filed under section 158BC. Penalty was imposable. A re computation of the undisclosed income was warranted. Penalty could be imposed only on the excess amounts determined at 15 per cent. of the undisclosed receipts, from that conceded in the returns filed under section158BC . Matter remanded for computation.