25. A holder of a Class A, B or C permit who wishes to carry on an activity in a new establishment in Québec for the carrying on of activities already authorized by his permit shall first apply for modification of his permit; with his application for modification, he shall pay the fees exigible under section 21 for each establishment covered by the application. Notwithstanding the foregoing, if the application is made during the last 18 months of the permit’s term, the fees are fixed at one-half of the fees prescribed in section 21.