Illinois
For Illinois, employer covered when is "Employer" means any business enterprise that employs: (1) 75 or more employees, excluding part-time employees; or (2) 75 or more employees who in the aggregate work at least 4,000 hours per week (exclusive of hours of overtime); notice triggered by is a plant closing — a shutdown resulting in an employment loss at the single site of employment during any 30-day period for 50 or more employees excluding any part-time employees — or a mass layoff resulting in an employment loss during any 30-day period for at least 33% of the employees and at least 25 employees (excluding part-time), or at least 250 employees; statute is 820 ILCS 65/5, verified against its source on 2026-08-18.
- State
- Illinois our reading
- Employer covered when
- "Employer" means any business enterprise that employs: (1) 75 or more employees, excluding part-time employees; or (2) 75 or more employees who in the aggregate work at least 4,000 hours per week (exclusive of hours of overtime) verified
- Notice triggered by
- a plant closing — a shutdown resulting in an employment loss at the single site of employment during any 30-day period for 50 or more employees excluding any part-time employees — or a mass layoff resulting in an employment loss during any 30-day period for at least 33% of the employees and at least 25 employees (excluding part-time), or at least 250 employees verified
- Statute
- 820 ILCS 65/5 verified
- Notice period
- An employer may not order a mass layoff, relocation, or employment loss unless, 60 days before the order takes effect, the employer gives written notice of the order per ilga.gov
Values marked our reading are our classification of what the source says — the source does not print them in those words. The quote below is the evidence for each one; judge it yourself.
What the source says
(c) "Employer" means any business enterprise that employs: (1) 75 or more employees, excluding part-time | | employees; or | | (2) 75 or more employees who in the aggregate work at | | least 4,000 hours per week (exclusive of hours of overtime). | | (d) "Mass layoff" means a reduction in force which: (1) is not the result of a plant closing; and (2) results in an employment loss at the single site | | of employment during any 30-day period for: | | (A) at least 33% of the employees (excluding any | | part-time employees) and at least 25 employees (excluding any part-time employees); or | | (B) at least 250 employees (excluding any | | part-time employees). | | (e) "Part-time employee" means an employee who is employed for an average of fewer than 20 hours per week or who has been employed for fewer than 6 of the 12 months preceding the date on which notice is required. (f) "Plant closing" means the permanent or temporary shutdown of a single site of employment, or one or more facilities or operating units within a single site of employment, if the shutdown results in an employment loss at the single site of employment during any 30-day period for 50 or more employees excluding any part-time employees.
— ilga.gov, retrieved 2026-08-18
Sources disagree
More than one authority states this, and they do not state the same thing. Both are reproduced with the source each came from — deciding between them is yours, not ours.
Statute
ilga.gov says statute is 820 ILCS 65/5, as of 2026-08-18.
(c) "Employer" means any business enterprise that employs: (1) 75 or more employees, excluding part-time | | employees; or | | (2) 75 or more employees who in the aggregate work at | | least 4,000 hours per week (exclusive of hours of overtime). | | (d) "Mass layoff" means a reduction in force which: (1) is not the result of a plant closing; and (2) results in an employment loss at the single site | | of employment during any 30-day period for: | | (A) at least 33% of the employees (excluding any | | part-time employees) and at least 25 employees (excluding any part-time employees); or | | (B) at least 250 employees (excluding any | | part-time employees). | | (e) "Part-time employee" means an employee who is employed for an average of fewer than 20 hours per week or who has been employed for fewer than 6 of the 12 months preceding the date on which notice is required. (f) "Plant closing" means the permanent or temporary shutdown of a single site of employment, or one or more facilities or operating units within a single site of employment, if the shutdown results in an employment loss at the single site of employment during any 30-day period for 50 or more employees excluding any part-time employees.
https://www.ilga.gov/legislation/ilcs/documents/082000650K5.htm
ilga.gov says statute is 820 ILCS 65/10, as of 2026-08-18.
(a) An employer may not order a mass layoff, relocation, or employment loss unless, 60 days before the order takes effect, the employer gives written notice of the order
https://www.ilga.gov/legislation/ilcs/documents/082000650K10.htm