40 ILCS 5/17-130.1
An Employer and the Board may make and may incur an obligation to make contributions on behalf of its employees in an amount not to exceed the employee contributions required by Section 17-130 for all compensation earned after September 21, 1981. If the Employer or the Board of Education determines not to make such contributions or incur an obligation to make such contributions, the amount that it could have contributed on behalf of its employees shall continue to be deducted from salary. If contributions are made by an Employer or the Board on behalf of its employees they shall be treated as employer contributions in determining tax treatment under the United States Internal Revenue Code. An Employer or the Board may make these contributions on behalf of its employees by a reduction in the cash salary of the employee or by an offset against a future salary increase or by a combination of a reduction in salary and offset against a future salary increase. An Employer or the Board shall pay these employee contributions from the same source of funds which is used in paying salary to the employee, or it may also or alternatively make such contributions from the proceeds of the tax authorized by Section 34-60 of the School Code. Such employee contributions shall be treated for all purposes of this Article 17 in the same manner and to the same extent as employee contributions made by employees and deducted from salary; provided, however, that contributions made by the Board of Education on behalf of its employees which are to be paid from the proceeds of the tax, as provided in Section 34-60 of the School Code, shall not be treated as teachers' pension contributions for the purposes of Section 17-132 of the Illinois Pension Code, and provided further, that contributions which are made by the Board of Education on behalf of its employees shall not be treated as a pension or retirement obligation of the Board of Education for purposes of Section 12 of "An Act in relation to State revenue sharing with local governmental entities", approved July 31, 1969.
40 ILCS 5/17-130.1