The new parish of Rhyl was assigned to the No. 1 ("St. Asaph") sub-district of the St. Asaph Registration District, which was co-extensive with the St. Asaph poor law Union.
In the GRO indexes to civil registration, entries for Rhyl are found under:
- Years 1837 - 1851: St. Asaph XXVII. nnn
- Years 1852 - 1946: St. Asaph 11b. nnn
(GRO index references have no relevance at the local Superintendent Registrar's Office)