820 ILCS 405/1402
If the Director deems an employer's report of wages paid to each of his workers for any period which begins on or after January 1, 1982, insufficient, he shall notify the employer to file a sufficient report. If the employer fails to file such sufficient report within 30 days after the mailing of the notice to him, he shall, in addition to any sum otherwise payable by him under the provisions of this Act, pay to the Department as a penalty a sum determined in accordance with the provisions of the first paragraph of this subsection, for each month or part thereof of such failure to file such sufficient report after the date of the notice.
For wages paid in calendar years prior to 1988, the penalty or penalties which accrue under the two foregoing paragraphs with respect to a report for any period shall not be less than $100, and shall not exceed the lesser of (1) $10 for each $10,000 or fraction thereof of the total wages for insured work paid during the period or (2) $5,000. For wages paid in calendar years after 1987, the penalty or penalties which accrue under the 2 foregoing paragraphs with respect to a report for any period shall not be less than $50, and shall not exceed the lesser of (1) $10 for each $10,000 or fraction of the total wages for insured work paid during the period or (2) $5,000. With respect to an employer who has elected to file reports of wages on an annual basis pursuant to Section 1400.2, for purposes of calculating the minimum penalty prescribed by this Section for failure to file the reports on a timely basis, a calendar year shall constitute a single period. For reports of wages paid after 1986, the Director shall not, however, impose a penalty pursuant to either of the two foregoing paragraphs on any employer who can prove within 30 working days after the mailing of a notice of his failure to file such a report, that (1) the failure to file the report is his first such failure during the previous 20 consecutive calendar quarters, and (2) the amount of the total contributions due for the calendar quarter of such report (or, in the case of an employer who is required to file the reports on a monthly basis, the amount of the total contributions due for the calendar quarter that includes the month of such report) is less than $500.
For any month which begins on or after January 1, 2013, a report of the wages paid to each of an employer's workers shall be due on or before the last day of the month next following the calendar month in which the wages were paid if the employer is required to report such wages electronically pursuant to the regulations of the Director; otherwise a report of the wages paid to each of the employer's workers shall be due on or before the last day of the month next following the calendar quarter in which the wages were paid.
Any employer who willfully fails to pay any contribution or part thereof, based upon wages paid prior to 1987, when required by the provisions of this Act and the regulations of the Director, with intent to defraud the Director, shall in addition to such contribution or part thereof pay to the Department a penalty equal to 50 percent of the amount of such contribution or part thereof, as the case may be, provided that the penalty shall not be less than $200.
Any employer who willfully fails to pay any contribution or part thereof, based upon wages paid in 1987 and in each calendar year thereafter, when required by the provisions of this Act and the regulations of the Director, with intent to defraud the Director, shall in addition to such contribution or part thereof pay to the Department a penalty equal to 60% of the amount of such contribution or part thereof, as the case may be, provided that the penalty shall not be less than $400.
However, all or part of any penalty may be waived by the Director for good cause shown.
820 ILCS 405/1402