The tax herein required to be collected by any delivering supplier maintaining a place of business in this State, and any such tax collected by that person, shall constitute a debt owed by that person to this State, provided, that the delivering supplier shall be allowed credit for such tax related to deliveries of electricity the charges for which are written off as uncollectible, and provided further, that if such charges are thereafter collected, the delivering supplier shall be obligated to remit such tax. For purposes of this Section, any partial payment not specifically identified by the purchaser shall be deemed to be for the delivery of electricity.
35 ILCS 640/2-8