(40 ILCS 5/16-129.1)
    Sec. 16-129.1. Optional increase in retirement annuity.
    (a) A member of the System may qualify for the augmented rate under subdivision (a)(B)(1) of Section 16-133 for all years of creditable service earned before July 1, 1998 by making the optional contribution specified in subsection (b). A member may not elect to qualify for the augmented rate for only a portion of his or her creditable service earned before July 1, 1998.
    (b) The contribution shall be an amount equal to 1.0% of the member's highest salary rate in the 4 consecutive school years immediately prior to but not including the school year in which the application occurs, multiplied by the number of years of creditable service earned by the member before July 1, 1998 or 20, whichever is less. This contribution shall be reduced by 1.0% of that salary rate for every 3 full years of creditable service earned by the member after June 30, 1998. The contribution shall be further reduced at the rate of 25% of the contribution (as reduced for service after June 30, 1998) for each year of the member's total creditable service in excess of 34 years. The contribution shall not in any event exceed 20% of that salary rate.
    The member shall pay to the System the amount of the contribution as calculated at the time of application under this Section. The amount of the contribution determined under this subsection shall be recalculated at the time of retirement, and if the System determines that the amount paid by the member exceeds the recalculated amount, the System shall refund the difference to the member with regular interest from the date of payment to the date of refund.
    The contribution required by this subsection shall be paid in one of the following ways or in a combination of the following ways that does not extend over more than 5 years:
        (i) in a lump sum on or before the date of retirement;
        (ii) in substantially equal installments over a
    
period of time not to exceed 5 years, as a deduction from salary in accordance with subsection (b) of Section 16-154;
        (iii) in substantially equal monthly installments
    
over a 24-month period, by reducing the annuitant's monthly benefit over a 24-month period by the amount of the otherwise applicable contribution. For federal and Illinois tax purposes, the monthly amount by which the annuitant's benefit is reduced shall not be treated as a contribution by the annuitant, but rather as a reduction of the annuitant's monthly benefit.
    (c) If the member fails to make the full contribution under this Section in a timely fashion, the payments made under this Section shall be refunded to the member, without interest. If the member dies before making the full contribution, the payments made under this Section, together with regular interest thereon, shall be refunded to the member's designated beneficiary for benefits under Section 16-138.
    (d) For purposes of this Section and subdivision (a)(B)(1) of Section 16-133, optional creditable service established by a member shall be deemed to have been earned at the time of the employment or other qualifying event upon which the service is based, rather than at the time the credit was established in this System.
    (e) The contributions required under this Section are the responsibility of the teacher and not the teacher's employer. However, an employer of teachers may, after the effective date of this amendatory Act of 1998, specifically agree, through collective bargaining or otherwise, to make the contributions required by this Section on behalf of those teachers.
    (f) A person who, on or after July 1, 1998 and before June 4, 1999, began receiving a retirement annuity calculated at the augmented rate may apply in writing to have the annuity recalculated to reflect the changes to this Section and Section 16-133 that were enacted in Public Act 91-17. The amount of any resulting decrease in the optional contribution shall be refunded to the annuitant, without interest. Any resulting increase in retirement annuity shall take effect on the next annuity payment date following the date of application under this subsection.
(Source: P.A. 92-416, eff. 8-17-01; 93-469, eff. 8-8-03.)