The Illinois Department of Revenue published a general information letter (ST25-0022-GIL) addressing whether tariffs are deductible when calculating how much sales tax they owe to the state. The state clarified that, for most retailers, tariffs are not deductible in calculating their owed sales tax and that tariffs paid by retailers are included in taxable gross receipts. 

The bottom line: If your business imports goods and pays the tariffs (even if separately itemized on customer invoices), those tariff costs must be included in your taxable receipts; but if your customer handles the importation and pays tariffs directly to the U.S. Customs, only the amount you charge the customer is taxable.