(2)substage for the purpose of collection of duty to be calculated annually and duty on excess deficiency. Wastage for the purpose of collection of duty on the excess as aforesaid shall be calculated annually, that is, at the end of the year for which the licence is in force;Provided that if it shall be proved to the satisfaction of the Excise Commissioner or of such officer as he may appoint, that such deficiency in excess of half percent (0.5%) has been caused by accident or other unavoidable cause, the duty on such deficiency may either be wholly or partly remitted at the direction of Excise Commissioner.
