R.I. Gen. Laws § 39-17-3
Every corporation that shall accept exclusive rights or franchises granted by ordinance or contract under the provisions of this chapter, shall make and render to the treasurer of the town or city granting the same, on or before the thirtieth day of January, April, July, and October in every year, returns, verified by the oath of its president or treasurer, of the gross earnings of the corporation within the town or city for the period of three (3) months next preceding the first day of January, April, July, and October in the same year, and shall at the time pay to the town or city treasurer, in full payment for the rights and franchises granted under this chapter, a special tax upon the gross earnings at a rate not exceeding three percent (3%) upon the gross earnings of the corporation within the town or city in that year.
R.I. Gen. Laws § 39-17-3