40 ILCS 5/6-170
The city shall contribute all amounts ordinarily contributed by it for annuity purposes for any fireman receiving ordinary disability benefit and the fireman shall receive credit therefor as though he were in active discharge of his duties during disability.
For each year, at least 1/3 of the total sum estimated annually by the board as necessary to provide ordinary disability benefits during the year shall be contributed by the firemen as follows:
Such amount (1/3 of said total sum) shall be prorated among all such firemen in proportion to the annual salary of each fireman, the percentage of each such annual salary which the sum related thereto shall constitute shall be ascertained, and a sum equal to a life percentage of each payment of such salary, but not less than 1/8 of 1% of each such payment, shall be deducted from each payment of salary.
The city shall contribute the balance of the total sum estimated annually as necessary to provide ordinary disability benefits during each year.
Whenever the balance in the ordinary disability reserve at the end of any calendar year, exclusive of employee contributions and city contributions for ordinary disability benefit purposes for such year, is sufficient to provide for all valid claims for ordinary disability benefits due for such year, such salary deductions for such year shall forthwith become the property of the respective firemen concerned. Any fireman from whose salary such deductions were made for such year may direct the board to transfer such deductions to the Gift Reserve to be used as he specifies in writing, or may otherwise direct the retirement board as to the disposition to be made of these deductions, excepting that they may not be credited to his account in the salary deduction reserve or in the annuity payment reserve; and the city shall not be required to contribute any amount for ordinary disability benefit purposes for such year.
40 ILCS 5/6-170