40 ILCS 5/3-125.1
Each police officer shall contribute to the pension fund the following percentages of salary for the periods stated: Beginning July 1, 1909 and prior to July 23, 1943, 1% (except that prior to July 1, 1921 not more than one dollar per month shall be deducted, and except that beginning July 1, 1921 and prior to July 1, 1927 not more than $2 per month shall be deducted); beginning July 23, 1943 and prior to July 20, 1949, 3%; beginning July 20, 1949 and prior to July 17, 1959, 5%; beginning July 17, 1959 and prior to July 1, 1971, 7%; beginning July 1, 1971 and prior to July 1, 1975, 7 1/2%; beginning July 1, 1975 and prior to January 1, 1987, 8 1/2%; beginning January 1, 1987, and prior to January 1, 2001, 9%; and beginning January 1, 2001, 9.91%. Such sums shall be paid or deducted monthly. Contribution to the self-managed plan shall be no less than 10% of salary.
"Salary" means the annual salary, including longevity, attached to the police officer's rank, as established by the municipality's appropriation ordinance, including any compensation for overtime which is included in the salary so established, but excluding any "overtime pay", "holiday pay", "bonus pay", "merit pay", or any other cash benefit not included in the salary so established.
40 ILCS 5/3-125.1