Transitional-year tax adjustments: increased thresholds, prorated depreciation and Board authority to prescribe revised amounts. The amendments expand proviso references in rule 1 and, in rule 3, permit increasing specified monetary limits during a transitional previous year where long-term capital gain arises from transfers spanning initial and later periods; they empower the Board to prescribe increases when multiple source-periods are included. The Table of amounts is replaced. Rules 4 and 5 adjust day-count thresholds for extended transitional years and require prorated depreciation allowances by months included. Rule 6's proviso mandates tax at the average rate on transitional-year income after excluding income already or to be included in the immediately relevant previous year(s).