R.I. Gen. Laws § 17-20-16: Time of casting vote.

Mail ballots may be cast in the manner provided by law on or before election day; provided, that no mail ballot shall be counted unless it is received by the state board not later than the time prescribed by § 17-18-11 for the closing of polling places on election day, except ballots cast under the provisions of § 17-20-6.1, which shall be counted if received by the state board by four o’clock p.m. (4:00) on the third day following a primary or four o’clock p.m. (4:00) on the seventh day following an election.