Ind. Code § 8-1-6-8
Each installment or required payment of the fee imposed by section 4 of this chapter becomes delinquent at midnight of the last day for payment thereof as provided in section 7 of this chapter. If a public utility has failed to pay, or has underpaid, the proper amount of any quarterly installment or payment, it shall pay a penalty to the commission of one percent (1%) of the amount so due on any quarterly installment or payment for each month or fraction thereof that such amount is unpaid. The commission may enforce the collection of any delinquent installment or payment, or portion thereof by legal action or in any other manner by which the collection of debts due the state of Indiana may be enforced under the laws of this state.
IC 8-1-6-8