Illinois’ back-to-school sales tax break provides relief for 10 daysThe state will slash its sales tax for 10 days this month. Illinois will slash its state sales tax on certain school supplies, clothing and shoes from Aug. 7 through Aug. 16. During that time, the state sales tax will drop to 1.25% from the usual 6.25%. The sales tax holiday is welcome relief for families that usually pay some of the highest sales taxes in the country. During the 355 days of the year with no back-to-school sales tax holiday, city of Chicago shoppers pay 10.5% sales tax, among the highest in the country.