40 ILCS 5/17-156.1
A teacher who retired prior to September 1, 1959 on service retirement pension who was at least 55 years of age at date of retirement and had at least 20 years of validated service shall be entitled to receive benefits under this Section.
These benefits shall be in an amount equal to 1-1/2% of the total of (1) the initial service retirement pension plus (2) any emeritus payment payable under Sections 34-86 and 34-87 (now repealed) of the School Code, multiplied by the number of full years on pension. This payment shall begin in January of 1970. An additional 1-1/2% shall be added in January of each year thereafter. Beginning January 1, 1972 the rate of increase in the service retirement pension each year shall be 2%. Beginning January 1, 1979, the rate of increase in the service retirement pension each year shall be 3%. Beginning January 1, 1990, all automatic annual increases payable under this Section shall be calculated as a percentage of the total pension payable at the time of the increase, including all increases previously granted under this Article, notwithstanding Section 17-157.
A pensioner who otherwise qualifies for the aforesaid benefit shall make a one-time payment of 1% of the final monthly average salary multiplied by the number of completed years of service forming the basis of his service retirement pension or, if the pension was not computed according to average salary as defined in Section 17-116, 1% of the monthly base pension multiplied by each complete year of service forming the basis of his service retirement pension. Unless the pensioner rejects the benefits of this Section, such sum shall be deducted from the pensioner's December 1969 pension check and shall not be refundable.
40 ILCS 5/17-156.1