1. (1) A utility may charge for late payments, consistent with its tariff, on the balance of any bill for service, which has not been paid in full within 20 calendar days of the date payment was due.

2. (2) A utility may not impose a late payment charge on any bill that is the subject of a pending complaint before the utility or the commission; provided, however, that a late payment charge may be imposed if the final resolution of the complaint directs payment of the disputed amount or any portion of it to the utility.

   (b) Other charges.

   Except as provided in this section, a utility may not charge any customer a late payment charge, penalty, fee, interest or other charge of any kind for any late payment or collection effort because the customer has failed to pay on time. Nothing in this section prevents a utility from imposing a reasonable charge for other lawful purposes, consistent with its tariff.

(a) Late payment charges.