70 ILCS 605/5-6
Notice of the hearing on the assessment roll shall be given in the manner and for the length of time provided in Section 4-22.
The commissioners shall, at least 10 days prior to the date fixed for hearing and within 4 days after the first publication of the notice, mail a copy of the notice (a) to each person named in the assessment roll as an owner of, or as having last paid the general taxes on, land being assessed and (b) to any other district or municipal corporation exercising drainage powers against which an assessment is being levied.
Any notice given by mail shall be sent first-class, with the postage thereon fully prepaid. The certificate of the chairperson or the affidavit of any other credible person affixed to a copy of the notice shall be sufficient evidence of the mailing of the notice.
However, with respect to land located within the boundaries of a municipality, the mailing of the notice required by this Section to the owner of such land or to the person having last paid the general taxes on such land shall be at the option of the commissioners.
70 ILCS 605/5-6