Advance payment of interest-tax requires staged instalments during the financial year with minimum payments and final reconciliation. Interest-tax for the assessment year is payable in advance during the preceding financial year by staged instalments: a minimum portion by 15 September, an increased minimum by 15 December reduced by earlier payments, and the balance by 15 March reduced by prior instalments; payments made on or before 31 March are treated as advance payments for that financial year.