Advance tax instalment schedule requires staged payments during the year, with presumptive taxpayers paying full advance tax at final instalment. Advance tax on current income must be paid in instalments under a prescribed timetable, with most assessees required to pay in four progressive instalments and presumptive assessees required to pay the whole advance tax by the final instalment date; each instalment is computed by reducing the total by amounts already paid, payments made by the last day of the financial year are treated as advance tax for that year, and where a demand notice is served after instalment dates the remaining liability is payable on the subsequent instalment dates.