A utility providing utility consolidated billing shall either purchase the receivables of a supplier or prorate customer payments between the utility and a supplier. The utility has the option of choosing whether its consolidated billing agreement includes the purchase of supplier receivables or the proration of customer payments. If the utility chooses the option of purchasing supplier receivables, supplier receivables shall be purchased with full and timely cost recovery for the utility under terms and conditions approved by the Commission. An early termination fee is not considered a commodity and is not subject to purchase as a receivable by the utility. If the utility chooses the option of prorating customer payments, a payment shall be allocated between the utility, supplier, and any other party in proportion to the percentage of the combined charges on the customer's total bill under terms and conditions approved by the Commission. If supplier receivables are not purchased by the utility, a utility shall bill for supplier charges and arrearages for a minimum of 90 days from the date a supplier receives final usage data from the utility. If supplier receivables are not purchased by the utility and the utility cancels a supplier's charges, the utility shall rebill the canceled supplier charges to the customer for at least 90 days after the bill adjustment.