If you look in the state statutes you will find that Chapter 31-3 deals with the Registration of Vehicles. Under Section 31-3-32, it is written that "every vehicle registration shall expire at midnight on the thirty-first (31st) day of March of each year, except that the director of the department of revenue, division of motor vehicles shall implement a staggered registration system and a staggered distribution system for fully reflective plates required to be on all vehicles."
In the past, the registration for all motor vehicles in Rhode Island expired in March of each year. A decision was made in the mid 1980s to begin a staggered registration system with passenger vehicle registration renewals due every two years. But DMV kept renewal of commercial and combination registrations due in March of each year. This decision was made, in part, because the registration fee for a commercial vehicle is based upon gross vehicle weight (GVW) and the registration fee is usually more expensive than for a passenger vehicle.
DMV currently maintains a staggered registration renewal schedule based on the last name of the person who registers the vehicle.
January A & B
February C & Farm vehicles
March Combination, commercial and commercial trailers
April D and non-commercial trailers
May E, F, G & antiques
June H, I J, radio operator, motorcycle, any numerical name
July K, L, taxi, jitney, school bus & public plates
August M & POW plates
September N, O, P, Q, campers and suburban plates
October R & S
November T, U, V, W, X, Y & Z
December Miscellaneous & special plate types
Miscellaneous plates include Disabled Veterans, State, City, Town, Police, Fire Apparatus, State/Federal Offices, Sheriff, State Police, Civil Defense, Senate, House, News Photographer, Police & State Police Motorcycles, Shrine, Registry, Racer Tow, Dealers, Bailee, Manufacturer, In-Transit or Transporter registrations.
Registration renewals may be processed by mail, DMV Drop Box or online at dmv.ri.gov.