| Umio Limited | Professional & scientific | 2008 |
| Unbounded Future Ltd | Information & communication | 2019 |
| Unciafer Ltd | Professional & scientific | 2020 |
| Uncomfortable Oxford C.I.C. | Administrative & support | 2019 |
| Under Construction (Geoff Barker) Limited | Construction | 2010 |
| Underrated Individuals Ltd | Information & communication | 2022 |
| Underwood Software Ltd | Information & communication | 2024 |
| Unequal Ltd | Professional & scientific | 2021 |
| UNI Barbers Oxford Ltd | Other services | 2025 |
| Unicol Audio Visual Limited | Real estate | 1973 |
| Unicol Engineering | Manufacturing | 1986 |
| Unicol Limited | Extraterritorial | 1995 |
| Unified Consortium Limited | Wholesale & retail | 2021 |
| Unified Dating Limited | Other services | 2015 |
| Unified Health Limited | Health & social care | 2025 |
| Uniflor Ltd | Professional & scientific | 2020 |
| Uniform Precision Tooling Limited | Manufacturing | 2022 |
| Uniheat (Oxford) Limited | Construction | 1972 |
| Uniheat Holdings Limited | Administrative & support | 2023 |
| Unimrkt Research Limited | Professional & scientific | 2023 |
| Union House 12-16 ST. Michaels Street Ltd | Real estate | 2024 |
| Unipart Accelerated Logistics Limited | Administrative & support | 2012 |
| Unipart Advanced Manufacturing Limited | Professional & scientific | 2018 |
| Unipart Construction Technologies Limited | Administrative & support | 2018 |
| Unipart Exports Limited | Wholesale & retail | 1981 |
| Unipart Fleet Services Limited | Transport & logistics | 1985 |
| Unipart Group Holdings Limited | Professional & scientific | 2018 |
| Unipart Group of Companies Limited | Professional & scientific | 1986 |
| Unipart International Holdings Limited | Professional & scientific | 1957 |
| Unipart Logistics Limited | Transport & logistics | 2001 |
| Unipart Manufacturing JV Holdings Limited | Professional & scientific | 2018 |
| Unipart North America Limited | Wholesale & retail | 1998 |
| Unipart Polymer and Composite Solutions Limited | Manufacturing | 2024 |
| Unipart Rail Holdings Limited | Professional & scientific | 1996 |
| Unipart Rail Limited | Transport & logistics | 1995 |
| Unipart Rail Logistics Limited | Extraterritorial | 2001 |
| Unipart Robotics Limited | Professional & scientific | 2023 |
| Unipart Security Solutions Limited | Administrative & support | 1986 |
| Unipart Service Company Limited | Extraterritorial | 1905 |
| Unique Drives and Roofing Limited | Construction | 2022 |
| Unique Gale Worldwide Corporation Limited | Manufacturing | 2025 |
| Unique Kudos Petroleum Ltd | Wholesale & retail | 2023 |
| Unique Properties Limited | Hospitality | 2014 |
| Unisoc Limited | Information & communication | 2025 |
| United Asian Baptist Church Oxford | Administrative & support | 2008 |
| United Broadcasting Networks Ltd | Wholesale & retail | 2017 |
| United Executive Ltd | Transport & logistics | 2018 |
| United Fashion Limited | Wholesale & retail | 2025 |
| United to Defeat Aging Limited | Manufacturing | 2021 |
| Unity Coffee Technologies Limited | Wholesale & retail | 2024 |
| Unity Construction and Management Ltd | Construction | 2025 |
| Univdevco Limited | Construction | 2019 |
| Universal Access and Power Plant Limited | Administrative & support | 1987 |
| Universal Business Finance Limited | Financial services | 2023 |
| Universal Hand Car Wash Ltd | Administrative & support | 2024 |
| Universal Logic Limited | Information & communication | 2026 |
| Universal Vehicle Rental Ltd | Administrative & support | 2026 |
| Universal Video Ltd | Administrative & support | 2015 |
| Universify Education | Education | 2016 |
| Universities & Colleges Christian Fellowship | Other services | 1944 |
| UNO (Swinton) Ltd | Professional & scientific | 1991 |
| Unplugged Consulting Limited | Information & communication | 2022 |
| Untold Story Video Limited | Information & communication | 2023 |
| Upadhya Properties Limited | Real estate | 2025 |
| Upbeat Music Limited | Education | 1999 |
| Upload Consulting Limited | Information & communication | 2024 |
| Upper Childown Limited | Financial services | 2018 |
| Upper Heaven Ltd | Hospitality | 2024 |
| Upper Road Kennington Residents Limited | Real estate | 1985 |
| Upstairs Downstairs Limited | Households | 1994 |
| Upstream Consulting Ltd | Professional & scientific | 1999 |
| Upstream Developments Limited | Construction | 1997 |
| Upstream Douglas Limited | Professional & scientific | 2005 |
| Upstream Holdings Limited | Real estate | 2005 |
| Uptime Global Limited | Professional & scientific | 2022 |
| Upton Mcgougan Limited | Construction | 1988 |
| Urban Landscapes (Oxfordshire) Limited | Administrative & support | 2021 |
| Urban Neuron Ltd | Information & communication | 2024 |
| Urban Picnic Catering LP | | 2013 |
| Urban Smart Power Ltd | Construction | 2025 |
| Urbandiva Boutique LP | | 2016 |
| Urbane Developments Ltd | Construction | 2018 |
| Urbane Lettings Ltd | Real estate | 2024 |
| Urbannest Online Ltd | Wholesale & retail | 2026 |
| Urbanserve Group Limited | Administrative & support | 2026 |
| Urbanship UK Limited | Wholesale & retail | 2025 |
| Urodx Ltd | Health & social care | 2025 |
| Ursa Minor UK Ltd | Arts & recreation | 2018 |
| Ursula Florido Consultancy Limited | Professional & scientific | 2024 |
| Urwin (Oxford) Limited | Real estate | 2006 |
| USE Jump Limited | Information & communication | 2026 |
| Usus Ltd | Wholesale & retail | 2025 |
| UTAK1 BIO Limited | Administrative & support | 2015 |
| Utel Oxford Ltd | Wholesale & retail | 2026 |
| UXI Sport Limited | Education | 2024 |
| V & S Management Services Ltd | Professional & scientific | 2020 |
| V One Gardening Limited | Administrative & support | 2025 |
| V Payroll & HR Solutions Ltd | Administrative & support | 2024 |
| V S (Oxford) Limited | Real estate | 2006 |
| V Stack Limited | Hospitality | 2020 |