68. Any person who has not previously been assessed by way of regular assessment under this Ordinance or the Income-tax Act, 1922 (XI of 1922), shall before the fifteenth day of June in each financial year, if his total income, subject to section 64(2), of the period which would be the income year for the immediately following assessment year is likely to exceed ¹[²[six] lakh taka], send to the Deputy Commissioner of Taxes an estimate of his total income and advance tax payable by him calculated in the manner laid down in section 65 and shall pay such amount on such dates specified in section 66 as have not expired by instalments which may be revised according to section 67(2).