R.I. Gen. Laws § 44-29-3: Filing of returns — Date due — Interest and penalty.

On or before the tenth day of the month next succeeding the month in which any taxes imposed by this chapter are collected, the seller shall pay the taxes to the tax administrator and at the same time shall file with him or her a return in a form the administrator may by regulation prescribe. If any taxes are not paid to the tax administrator when due, there is added to the taxes, and made a part of the taxes, interest at the annual rate provided by § 44-1-7 from the date when the taxes became due until the date of payment; if any return is not filed when due, there shall be added to the taxes, and made a part of the taxes, a ten percent (10%) penalty of the amount of taxes due, which penalty shall be in addition to any interest added.