The parish of Trewen is in the Launceston Registration District, and has been since 1st July 1837. There were sub-districts at Altarnun, Launceston, North Hill, North Petherwin and St Stephen-by-Launceston, but these are now all closed. Parishes within the district were: Altarnun, Boyton, Egloskerry, Laneast, Launceston, Lawhitton, Lewannick, Lezant, Northill, St. Mary Magdalene, St. Stephens by Launceston, St. Thomas the Apostle, St. Thomas Street, South Petherwin, Stokeclimsland, Tremaine, Treneglos, Tresmeer, Trewen, Warbstow.
The Superintendant Registrar can be contacted at: Hendra, Dunheved Road, Launceston, PL15 9JG. Tel: 01566 772464.