Ill. Admin. Code tit. 56 § 2765.326
There must be either a separation from the employer or a reduction in the work offered which causes the individual to become unemployed, as defined in Section 239 of the Act, for the employer to be the chargeable employer under Section 1502.1 of the Act.
Example: For six months, an individual is employed on a full time basis for Company A and, at the same time, works part time for Company B, both liable, contributing employers. The individual is laid off by Company A but does not have sufficient base period earnings to immediately file a valid claim for unemployment benefits. He remains employed on a less than full time basis by Company B for several months until the base periods change. He now meets the requirements of Section 500E of the Act for establishing a valid claim based on his base period earnings from both Company A and Company B. If the individual continues to work, without a reduction in the work offered by Company B and earns less than his weekly benefit amount, even though he has not worked for Company A for several months, Company A will be held to be liable for any benefit charges which might accrue as a result of benefit payments to this individual. This is because Company B, while it meets the 30 day requirement, did not cause the individual to become unemployed because it neither caused his separation nor reduced the work offered to him.
Ill. Admin. Code tit. 56, § 2765.326
Added at 13 Ill. Reg. 17410, effective October 30, 1989