215 ILCS 5/529.2
Whenever the Secretary shall, in accordance with the Act, present to the State a request for reimbursement under the Act, the Fund shall immediately assess all companies which, during the calendar year with respect to which reimbursement is requested by the Secretary, are engaged in writing property insurance in this State. The amount of each such company's assessment shall be calculated by multiplying the amount of the reimbursement requested by the Secretary by a fraction the numerator of which is the company's direct property insurance premiums earned in this State and the denominator of which is the aggregate of such premiums for all companies. Within 30 days following the end of each full calendar quarter, each company shall pay to the Fund an amount equal to one-twelfth of the company's assessment.
215 ILCS 5/529.2