5 ILCS 340/4.5
A State annuitant may authorize the withholding of a portion of his or her annuity or disability benefit for contribution to a maximum of 4 organizations described in paragraphs (b) and (c) of Section 3 of this Act. Upon written request of a State annuitant, a retirement system may deduct or direct the State Comptroller to deduct from the annuity or disability benefit of the State annuitant the amount specified in the written request for payment to the organization designated by the State annuitant. The retirement system may determine the timing for the deductions based on the retirement system's benefit processing schedule. The moneys so deducted shall be paid over promptly to the organizations designated by the State annuitant by means of warrants drawn by the retirement system or the State Comptroller against the fund from which the State annuitant is receiving his or her annuity or disability benefit.
Withholding under this Section may be terminated by the State annuitant at any time by filing a written direction with the retirement system.
Each retirement system may promulgate rules regarding the administration of this Section with respect to persons receiving an annuity or disability benefit from the retirement system.
5 ILCS 340/4.5