Summary assessment powers protect revenue by permitting immediate assessment and deeming person in charge liable when taxpayer unascertainable. A proper officer may, with prior permission of an Additional Commissioner or Joint Commissioner, proceed to summary assessment on any evidence showing tax liability where delay may adversely affect revenue and issue an assessment order; if the taxable person is unascertainable for supplies of goods, the person in charge of the goods is deemed the taxable person and liable to be assessed and to pay tax and other amounts; the Additional or Joint Commissioner may withdraw an erroneous summary order and direct follow-up under the regular reassessment procedure.