65 ILCS 5/6-5-1

Mayor, clerk, treasurer and alderpersons. The mayor, clerk, treasurer and alderpersons elected under the provisions of this Article 6 shall each receive for the performance of their respective duties annual salaries fixed by the city council. Such salaries shall not be increased or decreased during any term of office. They must be established six months prior to general municipal elections at which such officials are to be voted on.