65 ILCS 5/9-2-99
Except as otherwise provided in Section 9-2-113, no person obtaining contracts from the municipality and agreeing to be paid out of special assessments or special taxes, has any claim or lien upon the municipality in any event, except from the collection of special assessments or special taxes made or to be made for the work contracted for. However, the municipality shall cause collections and payments to be made with all reasonable diligence. If it appears that such an assessment or tax cannot be levied or collected, the municipality, nevertheless, is not in any way liable to a contractor in case of failure to collect the assessment or tax, but, so far as it can legally do so, with all reasonable diligence, it shall cause a valid assessment or assessments, or special taxes, to be levied and collected to defray the cost of the work until all contractors are fully paid. Any contractor is entitled to the summary relief of mandamus or injunction to enforce the provisions of this section.
The municipal treasurer shall keep a separate account of each special assessment warrant number, and of the money received thereunder.
65 ILCS 5/9-2-99