Unabsorbed depreciation and research capital expenditure can be carried forward when business income is insufficient. Allowable deductions under Profits and gains of business or profession include depreciation, capital expenditure on scientific research, and capital expenditure for promoting family planning among employees; where current-year business income is insufficient to absorb these deductions, the excess constitutes unabsorbed depreciation or unabsorbed capital expenditure on scientific research or family planning and may be carried forward to subsequent years for set off against future profits.