(1) Section 737 of the Principal Act is hereby amended -

(a) in subsection (1)(a), after the definition of "market value" by the insertion of the following definition:

"'relevant period' means -

(a) the period commencing on the date on which the first payment was made by or on behalf of an individual in respect of special investment units owned, whether jointly or otherwise, by that individual and ending on the fifth anniversary of that date, and

(b) each subsequent period of five years;",

(b) in subsection (3)(a), by the substitution in subparagraph (iii) for "at any time on or after the fifth anniversary of the date on which the first payment was made by or on behalf of that individual in respect of those units" of "on the date on which each relevant period ends", and

(c) in subsection (6), by the substitution of the following paragraph for paragraph (c):

"(c) Any income tax or capital gains tax chargeable in accordance with paragraph (b) shall be the amount of such tax, before it is reduced by any credit, relief or other deduction under the Tax Acts or the Capital Gains Tax Acts apart from this section, which is 20 per cent of income arising or chargeable gains accruing, as the case may be, to the scheme.".