The Illinois Sales Tax structure imposes two separate but complementary taxes upon the sale and use of tangible personal property. Section 2 of the Illinois Retailers’ Occupation Tax Act imposes a tax upon persons engaged in the business of selling at retail tangible personal property. The Complementary Use Tax is imposed by Section 3 of the Illinois Use Tax Act which imposes a tax upon the privilege of using in this state tangible personal property purchased at retail from a retailer.
The Retailers’ Occupation Tax is measured upon the retailer’s gross receipts and the retailer is statutorily required to collect the Complementary Use Tax from their customers. In effect, this reimburses the retailer for their Retailers’ Occupation Tax liability. If the use tax is not collected by the retailer, the customer is required to pay it directly to the State of Illinois.
Additional information about Sales Taxes can be found at Illinois Tax Information.