40 ILCS 5/16-185

(a) On July 1, 2003, the Employer's Contribution Reserve shall be renamed the Benefit Trust Reserve. The Benefit Trust Reserve shall serve as a clearing account for income and expenses of the System as well as transfers to and from the other reserve accounts established under this Article and adjustments thereto. (b) This Reserve shall be credited with all contributions, investment income, and other income received by the System, except as otherwise required by this Article. (c) This Reserve shall be charged with all benefits and refunds paid and all other expenses of the System, except as otherwise required under this Article.