(ii)an amount equal to seventy-five per cent. of the investment allowance to be actually allowed is debited to the profit and loss account of ][any previous year in respect of which the deduction is to be allowed under sub-section (3) or any earlier previous year (being a previous year not earlier than the year in which the ship or aircraft was acquired or the machinery or plant was installed or the ship, aircraft, machinery or plant was first put to use)] [ Substituted by Act 12 of 1990, Section 7, for " the previous year in respect of which the deduction is to be allowed" (w.r.e.f. 1.4.1976).] and credited to a reserve account (to be called the "Investment Allowance Reserve Account") to be utilised,-