This file contains the National Statistics UPRN Lookup (NSUL) for Great Britain as at October 2025. The NSUL relates the Unique Property Reference Number (UPRN) for each GB address from AddressBase® Epoch 121 to a range of current statutory administrative, electoral, health and other statistical geographies via 'best-fit' allocation from 2021 Census output areas (National Parks and Workplace Zones are exempt from 'best-fit' and use 'exact-fit' allocations). The NSUL is produced by ONS Geography, who provide geographic support to the Office for National Statistics (ONS) and geographic services used by other organisations. The NSUL 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 – 438 MB)NB. This Version 2 uses a revised methodology to correct issues in some geography allocations in the previously published version. A summary of this methodolgy is included in the user guide.The ZIP file also contains files listing those UPRNs which have been assigned a different Output Area, Workplace Zone or National Park, when comparing the previously published version of the NSUL to this revised version. There is also a file summarising these differences with counts and percentages by Local Authority District.