Section 18A(3) provides that : " Any person who has not hitherto been assessed shall, before the 15th day of March in each financial year, if his total income of the period which would be the previous year for an assessment for the financial year next following is likely to exceed six thousand rupees, send to the Income tax Officer an estimate of the tax payable by him on that part of his income to which the provisions of section 18 do not apply of the said previous year calculated in the manner laid down in sub section (1), and shall pay the amount, on such of the dates specified in that sub section as have not expired, by instalments which may be revised according to the proviso to sub section (2)." Section 18A(9) is as follows: " If the Income tax Officer, in the course of any proceedings in connection with the regular assessment, is satisfied that any assessee (a) has furnished under sub section (2) or sub section(3) estimates of the tax payable by him which he knew or had reason to believe to be untrue, or (b) has without reasonable cause failed to comply with the provisions of subsection (3), the assessee shall be deemed, in the case referred to in clause (a), to have deliberately furnished inaccurate particulars of his income, and in the case referred to in clause (b), to have failed to furnish the return of his total income; and the provisions of section 28, so far ' as may be, shall apply accordingly:".