| Unite Consume Ltd | Professional & scientific | 2025 |
| Unite Health Fitness HQ Limited | Arts & recreation | 2025 |
| Unite Health Fitness Limited | Arts & recreation | 2025 |
| Unite Housing Ltd | Households | 2023 |
| Unitec Communications Limited | Information & communication | 1998 |
| Unitech Data Systems Ltd | Information & communication | 2018 |
| United Commercial Trading(Uk) Limited | Water & waste | 2007 |
| United Financial Solutions Ltd | Financial services | 2017 |
| United Group Holdings Limited | Professional & scientific | 1993 |
| United Housing Solutions Limited | Real estate | 2015 |
| United Hydraulics Ltd | Administrative & support | 2026 |
| United Infrastructure Connected Limited | Information & communication | 2012 |
| United Infrastructure Energy Limited | Construction | 2012 |
| United Infrastructure Group Services Limited | Professional & scientific | 2025 |
| United Infrastructure Investment Limited | Construction | 2016 |
| United Infrastructure Limited | Financial services | 2023 |
| United Infrastructure Management Limited | Financial services | 2023 |
| United Infrastructure Power T&D Limited | Energy | 2019 |
| United Infrastructure Water Limited | Construction | 1991 |
| United Kingdom National Nuclear Laboratory Limited | Professional & scientific | 1999 |
| United Living EBT Limited | Financial services | 2020 |
| United Phosphorus Holdings UK Ltd | Financial services | 2019 |
| United Pipelines Limited | Professional & scientific | 1993 |
| United Utilities Bioresources Limited | Water & waste | 2016 |
| United Utilities Group PLC | Professional & scientific | 2008 |
| United Utilities Investment Partnership (NO.2) LP | | 2011 |
| United Utilities Water Finance PLC | Professional & scientific | 2014 |
| Units to LET (Northern) Limited | Real estate | 1982 |
| Units to LET (Yorkshire) Limited | Real estate | 1960 |
| Units to LET Limited | Households | 2014 |
| Unity Vision Consulting Limited | Information & communication | 2011 |
| Universal Atmosphere Processing UK Ltd | Professional & scientific | 2024 |
| Universal Business Installations Limited | Construction | 1997 |
| Universal Cell Therapeutics Ltd. | Manufacturing | 2017 |
| Universal Chemical Transport Limited | Transport & logistics | 2002 |
| Universal Fire Safety Limited | Administrative & support | 2026 |
| Universe Actuarial Limited | Administrative & support | 2021 |
| University Technical College Warrington | Education | 2013 |
| Unknown Engineering & Aerodynamics Ltd | Professional & scientific | 2021 |
| Unknown Group Ltd | Financial services | 2021 |
| Unknown Resourcing Ltd | Administrative & support | 2016 |
| Unmanned Limited | Professional & scientific | 2022 |
| Uno-Consult Limited | Professional & scientific | 2022 |
| Unseen Heights INT Ltd. | Professional & scientific | 2013 |
| Untapped Brands Limited | Wholesale & retail | 2021 |
| Unveilo Limited | Information & communication | 2024 |
| Uovo Technologies Limited | Professional & scientific | 2017 |
| UP West Limited | Administrative & support | 2012 |
| Uphost Ltd | Information & communication | 2018 |
| UPL Animal Health Holdings Limited | Agriculture & fishing | 2022 |
| UPL Crop Protection Investments UK Limited | Agriculture & fishing | 2022 |
| UPL Europe Ltd | Manufacturing | 1993 |
| UPL Health and Nutrition Science Holding Limited | Agriculture & fishing | 2022 |
| UPL Investments UK Limited | Agriculture & fishing | 2022 |
| Uplift and Clean Services Ltd | Administrative & support | 2025 |
| Uplift HR Ltd | Professional & scientific | 2023 |
| UPM Estates Limited | Households | 2020 |
| Upstream Technical Solutions Limited | Professional & scientific | 2017 |
| Uptime Commissioning Ltd | Administrative & support | 2025 |
| Uptoeleven Limited | Information & communication | 2016 |
| Upvc Windowcare Limited | Construction | 2007 |
| Urban Approved Project Management Ltd | Construction | 2026 |
| Urban Building and Developments Ltd | Other services | 2013 |
| Urban Building Projects Limited | Construction | 2004 |
| Urban Chemicals Limited | Wholesale & retail | 2023 |
| Urban Comb Ltd | Other services | 2025 |
| Urban Eco Valet Ltd | Other services | 2023 |
| Urban Energy Projects Limited | Professional & scientific | 2024 |
| Urban Feat Holdings Limited | Real estate | 2025 |
| Urban Feat Ltd | Real estate | 2020 |
| Urban Flavours 888 Ltd | Hospitality | 2025 |
| Urban Garden Projects Limited | Administrative & support | 2023 |
| Urban Gent Barbers Ltd | Other services | 2022 |
| Urban Green Services Ltd | Wholesale & retail | 2019 |
| Urban Groundscapes Limited | Administrative & support | 2020 |
| Urban Homes (NW) Limited | Construction | 2016 |
| Urban Life Manchester Limited | Construction | 2017 |
| Urban Luxe Stayz Ltd | Hospitality | 2026 |
| Urban Property Rentals Ltd | Real estate | 2016 |
| Urban Roofscapes Limited | Construction | 2017 |
| Urban Unwind Ltd | Households | 2025 |
| Urban ZOO Studios Limited | Information & communication | 2013 |
| Urbanbox Properties Limited | Real estate | 2020 |
| Urbanscape Group Limited | Financial services | 2026 |
| Uriel Energy Ltd | Professional & scientific | 2020 |
| Urooj Khan Ltd | Health & social care | 2018 |
| US Four Group Ltd | Wholesale & retail | 2018 |
| USE Hughes Limited | Other services | 2024 |
| USE Psychology Limited | Education | 2024 |
| Used Coach Sales Ltd | Wholesale & retail | 2010 |
| Usha Engineers Limited | Administrative & support | 2013 |
| Usman Solutions Limited | Administrative & support | 2025 |
| Uticarisk Limited | Construction | 2022 |
| Utilities 4U (NW) Ltd | Administrative & support | 2022 |
| Utility Connections (UK) Limited | Administrative & support | 2019 |
| Utility Connections Limited | Financial services | 2010 |
| Utility Infrastructure Group Ltd | Financial services | 2019 |
| Utility Infrastructure Group Trustee Limited | Administrative & support | 2021 |
| UTILITY360 Ltd | Administrative & support | 2010 |
| Uxlabs Limited | Information & communication | 2005 |