R.I. Gen. Laws § 44-13-6: Due date of annual return.

Every corporation shall file a return with the tax administrator on or before March 1 of each year. For tax years beginning after December 31, 2015, a return, in the form and containing the information as the tax administrator may prescribe, shall be filed with the tax administrator by every corporation and shall be filed on or before the date its federal tax return is due to be filed, without regard to extension.