110 ILCS 992/7-15

An EISA must specify that the maximum amount that a consumer could be required to pay under the EISA will not result in a consumer ever being required to pay an effective annual percentage rate that is greater than 9% or the high yield of the 10-year United States Constant Maturity Treasury Notes auctioned at the final auction held before the current calendar year in which the EISA is originated plus 6%, whichever is greater. If at any time the EISA provider accepts a payment of an amount that would cause the limit in this Section to apply, the EISA provider shall, within 20 calendar days, refund any amounts necessary to ensure that the consumer's payments do not result in an effective annual percentage rate that is greater than the limit specified in this Section.