Rulemaking power under the Income-tax Act authorises broad procedural and substantive tax regulations, with limited retrospectivity. Section 295 vests the Board, under Central Government control, with a broad rulemaking power to prescribe procedural and substantive matters for implementing the Income-tax Act, including income ascertainment, valuation of perquisites, depreciation, conditions for allowance of expenditures, filing and PAN procedures, electronic returns, appeal and refund processes, authority designations, and methods for estimating income where ascertainment is impracticable; it also permits retrospective rules subject to a safeguard against prejudicial effect on assessees.