Summary assessment powers protect revenue; officers may assess and deem person in charge liable when taxable person unascertainable. Proper officers, with prior permission of an Additional or Joint Commissioner, may make a summary assessment and issue an assessment order when evidence of tax liability emerges and delay may harm revenue; if the taxable person is unascertainable for goods, the person in charge is deemed the taxable person and liable. The Additional or Joint Commissioner may withdraw an erroneous summary order on application within thirty days or on their own motion and refer the matter to the regular assessment procedure.