70 ILCS 2405/22a.31
At any time after the bids have been received pursuant to the provisions of this Act, if it appears to the satisfaction of the committee of local improvements that the first assessment is insufficient to pay the contract price or the bonds or vouchers issued or to be issued in payment of the contract price, together with the amount required to pay the accruing interest thereon, the committee shall make and file an estimate of the amount of the deficiency. Thereupon a second or supplemental assessment for the estimated deficiency of the cost of the work and interest may be made in the same manner as nearly as may be as in the first assessment and so on until sufficient money has been realized to pay for the improvement and the interest. Alternatively, the district's board may, pursuant to a new ordinance which need not be initiated by the committee, file a petition with the court to assess all or any part of the deficiency against the district on account of public benefit whereupon the court shall enter judgment in accordance with the petition. It shall be no objection to the supplemental assessment that the prior assessment has been levied, adjudicated and collected.
If too large a sum is raised at any time, the excess shall be abated in accordance with Section 22a.48 of this Act. If the estimated deficiency exceeds 20% of the original estimate, no contract shall be awarded until a public hearing has been held on the supplemental proceeding in like manner as in the original proceedings unless the board files a petition to assess the entire deficiency against the district on account of the public benefit as above provided. More than one supplemental assessment may be levied to meet a deficiency.
The petitioner, in case it so elects, may dismiss the petition and vacate the judgment of confirmation at any time after the judgment of confirmation is rendered and begin new proceedings for the same or a different improvement as provided in Section 22a.29.
70 ILCS 2405/22a.31