This file contains the ONS UPRN Directory (ONSUD) for Great Britain as at May 2018. The ONSUD relates the Unique Property Reference Number (UPRN) for each GB address from AddressBase® Epoch 57 to a range of current statutory administrative, electoral, health and other statistical geographies. The ONSUD is produced by ONS Geography, who provide geographic support to the Office for National Statistics (ONS) and geographic services used by other organisations. The ONSUD is issued every 6 weeks and is designed to complement the Ordnance Survey AddressBase® product. For further technical information about this file, please refer to the User Guide document contained within the downloadable zip file. Please note that this product contains Royal Mail, Gridlink, Ordnance Survey and ONS Intellectual Property Rights. (File Size - 448 MB)