If the ¹ [Assessing Officer] in the course of any proceedings under this Act is satisfied that any person has failed to comply with a notice under sub-section (1) of section 9, he may direct that such person shall pay, by way of penalty, in addition to any tax payable by him, a sum which shall not be less than ten per cent. but which shall not exceed fifty per cent. of the amount of the tax, if any, which would have been avoided if the chargeable expenditure returned by such person had been accepted as the correct chargeable expenditure.