55 ILCS 5/5-32057
The Committee before crediting of the excess as provided for in Section 5-32043, shall estimate an amount as authorized in this Division sufficient to make up any probable deficiency of interest, in the event that from any cause, collections of interest may provide insufficient to meet the interest to be paid on the bonds until they mature as provided in this Division. This estimated amount shall be deducted out of the installments as an item of expense before crediting rebates of excess as directed in this Division, and shall be used for no other purpose than to make up such a deficiency until the bonds are fully paid, both principal and interest. Any balance remaining of this estimated amount after the principal and interest of the bonds are fully paid may be used to reimburse the county fund for any advance made from this fund on account of costs of the special assessment or other expenses of the improvement for which the special assessment is levied.
55 ILCS 5/5-32057