Tax on income of new manufacturing companies: optional concessional rates subject to strict eligibility and irrevocable exercise. An optional tax regime permits a newly established domestic company engaged in manufacture or production to compute tax at concessional rates for manufacturing income while non manufacturing income and certain capital gains attract higher rates; the option must be validly exercised by the prescribed due date, is irrevocable, applies to subsequent years, and becomes invalid if eligibility conditions cease. Total income is computed excluding specified deductions and without setting off certain losses or unabsorbed depreciation, which are treated as having been given full effect to in future years; in amalgamations the option continues only if conditions remain fulfilled.