5 ILCS 365/3

Whenever a Department whose payroll is processed by the Comptroller, or an Office other than the Comptroller, is authorized in writing by a State employee or annuitant to withhold a specified portion of such employee's or annuitant's salary, wages or annuity for a designated period of time for any one or more of the purposes specified in Section 4, such Department shall direct the Comptroller to withhold and such Office other than the Comptroller shall withhold from such employee's salary, wages or annuity for each pay period the amount specified in the authorization during the period of time therein designated.