Revised interest rate applies to the portion of interest accruing after the specified cutoff where periods straddle that date. Interest under the Income-tax Act, Wealth-tax Act, Gift-tax Act, Companies (Profits) Surtax Act and Interest Tax Act for any period commencing on or before 30th September, 1984 and ending after that date is declared to be calculated, for the portion of the period after that date, at the rate of fifteen per cent per annum.