Extension of deduction period under section 80-I increases the qualifying term to nine years for eligible undertakings. Amendment to section 80-I replaces the four-year qualifying period with a nine-year qualifying period in sub-sections (2)(iii) and (3)(iii), and advances the transitional cut-off in sub-section (4)(iv) from 1st April, 1985 to 1st April, 1990, thereby extending the duration of the specified tax consequence and modifying the applicability window for transitional provisions.