40 ILCS 5/3-127
The board shall establish and maintain a reserve to insure the payment of all obligations incurred under this Article excluding retirement annuities established under Section 3-109.3. The reserve to be accumulated shall be equal to the estimated total actuarial requirements of the fund.
If a pension fund has a reserve of less than the accrued liabilities of the fund, the board of the pension fund, in making its annual report to the city council or board of trustees of the municipality, shall designate the amount, calculated as a level percentage of payroll, needed annually to insure the accumulation of the reserve to the level of the fund's accrued liabilities over a period of 40 years from July 1, 1993 for pension funds then in operation, or from the date of establishment in the case of a fund created thereafter, so that the necessary reserves will be attained over such a period.
40 ILCS 5/3-127