Section 30 of the Principal Act is hereby amended in subsection (4) by the substitution of the following paragraphs for paragraph (a):
(i) In relation to any taxable period ending before the 1st day of May, 1998, an estimation or assessment of tax under section 22 or 23 may, subject to subparagraph (ii), be made at any time not later than ten years after the end of the taxable period to which the estimate or assessment relates or, where the period in respect of which the estimate or assessment is made consists of two or more taxable periods, after the end of the earlier or earliest taxable period comprised in such period.
(ii) In relation to any taxable period commencing on or after the 1st day of May, 1998, and on or after the 1st day of May, 1999, in relation to any other taxable period, an estimation or assessment of tax under section 22 or 23 may be made at any time not later than six years after the end of the taxable period to which the estimate or assessment relates or