Deduction restriction under section 80-IA: excludes enterprises commencing development or operation and maintenance of infrastructure after the specified commencement date. The amendment introduces a commencement-based exclusion under section 80-IA, providing that the deduction for enterprises engaged in development or operation and maintenance of infrastructure facilities shall not apply to enterprises that start such development or operation and maintenance on or after the statutory commencement date, thereby narrowing eligibility for the deduction for assessment years following that date.