(3) Subject to this section, every person shall pay to the Comptroller on or before 25 March, 25 June and 25 September respectively, in each year of income, an amount equal to 1/3 of the tax estimated by him or her at the rates set out in Schedule 5 on his or her estimated chargeable income for the year and, on or before 31 March in the following year, or where, in the case of a company, its financial year does not commence in the month of January, within 3 months after the end of its financial year, the remainder of the tax as estimated by him or her.