40 ILCS 5/9-220.1
A member of the General Assembly with service credit in the Fund may establish service credit in the Fund for up to 24 months, during each of which he or she worked for at least one but fewer than 15 days, by purchasing service credit for the number of days needed to bring the total of days worked in each such month up to 15. To establish this credit, the member must pay to the Fund before January 1, 1998 an amount equal to (1) employee contributions based on the number of days for which credit is being purchased, the rate of compensation received by the applicant for the time actually worked during that month, and the rate of contribution in effect for the applicant during that month; plus (2) an amount representing employer contributions, equal to the amount specified in item (1); plus (3) interest on the amounts specified in items (1) and (2) at the rate of 6% per annum, compounded annually, from the date of service to the date of payment. This Section is not limited to persons in service under this Article on or after the effective date of this amendatory Act of 1997.
40 ILCS 5/9-220.1