R.I. Gen. Laws § 44-19-20: Interest and penalties on delinquent payments.

Any person who fails to pay any tax to the state or any amount of tax required to be collected and paid to the state, except amounts of determinations made by the tax administrator under §§ 44-19-11 — 44-19-14 within the required time shall pay a penalty of ten percent (10%) of the tax or amount of the tax, in addition to the tax or amount of the tax, plus interest at the annual rate provided by § 44-1-7 from the date on which the tax or amount of the tax required to be collected became due and payable to the state until date of payment.