35 ILCS 110/3-40
The tax imposed by this Act shall be collected at the time of purchase in the manner prescribed by the Department from the user by a serviceman maintaining a place of business in this State or by a serviceman authorized by the Department under Section 7 of this Act, and the tax shall be remitted to the Department as provided in Section 9 of this Act.
The tax imposed by this Act that is not paid to a serviceman under this Section shall be paid to the Department directly by any person using the property within this State as provided in Section 10 of this Act.
If a serviceman collects Service Use Tax measured by receipts or selling prices that are not subject to Service Use Tax, or if a serviceman, in collecting Service Use Tax measured by receipts or selling prices that are subject to tax under this Act, collects more from the purchaser than the required amount of the Service Use Tax on the transaction, the purchaser shall have a legal right to claim a refund of that amount from the serviceman. If, however, that amount is not refunded to the purchaser for any reason, the serviceman is liable to pay that amount to the Department. This paragraph does not apply to an amount collected by the serviceman as Service Use Tax on receipts or selling prices that are subject to tax under this Act as long as the collection is made in compliance with the tax collection brackets prescribed by the Department in its rules and regulations.
35 ILCS 110/3-40