R.I. Gen. Laws § 44-7-24

No legal entity created by the general assembly, which is authorized to collect taxes, fees, assessments, rates, or other charges, including, but not limited to the Providence Water Supply Board and the city of Providence, shall refuse to accept cash-in-hand in payment of taxes, fees, assessments, rates, charges, or any other liability. Any legislatively created body shall be open for the collection of taxes, fees, assessments, rates, and charges during reasonable business hours. Failure of any legislatively created body to accept from any person cash-in-hand in payment of those liabilities set forth in this section shall discharge that person from the duty to pay that liability.