Reopening time limits extended where a transfer pricing reference is pending, suspending limitation timelines during such references. Section 153 is amended to extend and adjust limitation periods for reopening assessments by substituting earlier date ranges and inserting transitional provisos that lengthen the period for reopening where a transfer pricing reference is pending or made during assessment proceedings. The amendments also expand exclusion periods in Explanation 1, increasing one exclusion from six months to one year and adding an exclusion covering the interval while a reference concerning impermissible avoidance arrangements is pending, thereby suspending limitation timelines during such references and related orders.