The MBTA plans to start offering late-night bus service in July.



An official request for vendors to make offers to run the service is on file with the state. The document says the MBTA is looking for a company to provide service along a fixed bus route from Mattapan Square, through downtown Boston, East Boston and Revere.



The buses would run every 30 minutes between 1 a.m. and 4:15 a.m. Fares will not be collected during a nine month trial period during which MBTA officials plan to gather data on ridership.



The contractor would have to provide vehicles, drivers, maintenance and storage for six buses.



The T wants to begin the trial in July for nine months and will decide on whether to make it permanent later.