Development rebate changes limit allowance for plant and machinery by use and location, tightening exclusions for office and residential installations. The amendment substitutes clause (iii) of Section 33 to apply graded percentage allowances for plant and machinery depending on installation date and business purpose, including special rates for coal-mining and for manufacture or production of items in the Fifth Schedule; it expands subsection (2) cross-references to related allowance provisions and inserts a new subsection denying any development rebate for machinery or plant installed after 31 March 1965 in office premises or residential accommodation, including guest houses.