| Unicus Property Investment Limited | Real estate | 2024 |
| Unidrugs Limited | Wholesale & retail | 2001 |
| Unifiedliving Property Ltd | Construction | 2020 |
| Unify IT Services Limited | Information & communication | 2018 |
| Unify Utilities Ltd | Professional & scientific | 2025 |
| Unigigster Limited | Information & communication | 2020 |
| Unigma Ltd | Wholesale & retail | 2024 |
| Unik Interiors Ltd | Construction | 2023 |
| Uniken Europe Ltd | Information & communication | 2019 |
| Unilet (Milton Keynes) Limited | Real estate | 1999 |
| Uniniche Ltd | Wholesale & retail | 2025 |
| Uninterrupted Power Group Ltd | Financial services | 2017 |
| Uninterrupted Power Solutions Ltd | Administrative & support | 2001 |
| Union Trucks Limited | Wholesale & retail | 1956 |
| Unipro Technology Ltd | Information & communication | 2007 |
| Uniq Tidy Ltd | Administrative & support | 2026 |
| Unique Autocentre Limited | Wholesale & retail | 2012 |
| Unique Brass Finishes Ltd | Manufacturing | 2013 |
| Unique Car Services Ltd | Wholesale & retail | 2002 |
| Unique Corporate Property Management Limited | Real estate | 2017 |
| Unique Driveways MK Ltd | Administrative & support | 2021 |
| Unique Elite Cleaning Services Limited | Administrative & support | 2025 |
| Unique Estates Ltd | Real estate | 2024 |
| Unique Global Recruitment Consultancies Limited | Administrative & support | 2025 |
| Unique Housing Services Ltd | Other services | 2024 |
| Unique Line Cargo Ltd | Wholesale & retail | 2020 |
| Unique Link Solution Ltd | Real estate | 2019 |
| Unique Renovation Systems Ltd | Construction | 2019 |
| Unique Strategies Ltd | Professional & scientific | 2024 |
| UNIQUE24 Care Services Limited | Health & social care | 2022 |
| Uniqueallied Limited | Real estate | 1997 |
| Uniquec Properties Ltd | Real estate | 2026 |
| Uniquecapture Ltd | Professional & scientific | 2010 |
| Uniqueccc Ltd | Real estate | 2020 |
| Uniquely Premium Limited | Manufacturing | 2023 |
| Uniqueness Couture Ltd. | Health & social care | 2015 |
| Unirama Intl Ltd | Wholesale & retail | 2023 |
| Unisys Europe Limited | Information & communication | 2015 |
| Unisys European Services Limited | Professional & scientific | 2000 |
| Unisys Finance Limited | Financial services | 1998 |
| Unisys Group Services Limited | Professional & scientific | 1942 |
| Unisys Holdings | Professional & scientific | 1987 |
| Unisys Limited | Information & communication | 1909 |
| Unisys Payment Services Limited | Financial services | 1994 |
| Unisys Pension Scheme Trustee Limited | Extraterritorial | 2006 |
| Unisys Treasury Services Limited | Professional & scientific | 1999 |
| Unisys UK Pension Trustee Limited | Administrative & support | 2006 |
| Unit 18 Automotive Ltd | Wholesale & retail | 2017 |
| UNIT6 Group Ltd | Other services | 2009 |
| Unite Medical Limited | Administrative & support | 2013 |
| United Authors Publishing Limited | Information & communication | 2010 |
| United Emphire Shipping Ltd | Transport & logistics | 2024 |
| United Events Limited | Information & communication | 2026 |
| United Flavour Limited | Professional & scientific | 2025 |
| United Halal Butchers and Supermarket Ltd | Wholesale & retail | 2023 |
| United Minimart Ltd | Wholesale & retail | 2022 |
| United Quest Limited | Information & communication | 2015 |
| United Umuadaigbo Ambassadors Club Global Ltd | Other services | 2025 |
| United Umuadaigbo Club Global Ltd | Other services | 2025 |
| United Umuadaigbo Club International (UK Chapter) Ltd | Other services | 2020 |
| United World Publishing House PTE. Ltd. | Wholesale & retail | 2025 |
| Unitim Trading Limited | Wholesale & retail | 2019 |
| Unitronix UK Limited | Wholesale & retail | 2015 |
| Unity Fibre Ltd | Construction | 2025 |
| Unity Life Ventures Ltd | Professional & scientific | 2025 |
| Unity Purpose Investments Ltd | Real estate | 2020 |
| Unity Ventures Property Ltd | Real estate | 2025 |
| Unityalloys Limited | Wholesale & retail | 2025 |
| Unitymk | Hospitality | 2012 |
| Universal Blinds Limited | Manufacturing | 2005 |
| Universal Businesses Network Ltd | Administrative & support | 2023 |
| Universal Development Network CIC | Transport & logistics | 2024 |
| Universal Food Solutions Ltd | Financial services | 2021 |
| Universal Media (London) Ltd | Professional & scientific | 2018 |
| Universal Packaging Ltd | Hospitality | 2020 |
| Universal Publishing House PTE. Ltd. | Wholesale & retail | 2024 |
| Universal Science (UK) Limited | Manufacturing | 2011 |
| Universal Support & Living Ltd | Real estate | 2023 |
| Universal Transfers MK Ltd | Transport & logistics | 2026 |
| Universal Wholesale Ltd | Wholesale & retail | 2019 |
| Universe of Abundance Ltd | Professional & scientific | 2022 |
| Unknown Seller Limited | Wholesale & retail | 2021 |
| Unlimited Escape Ltd | Manufacturing | 2026 |
| Unlock Drama CIC | Education | 2020 |
| Unlocked Identity Ltd | Education | 2025 |
| Unmanned Tech Limited | Professional & scientific | 2017 |
| UNO Estate Ltd | Real estate | 2019 |
| Unruly Talent Lifestyle Consultancy Ltd | Professional & scientific | 2022 |
| Unsolved Crimes Specialists -UCS Limited | Administrative & support | 2024 |
| UP and UP Life Ltd | Wholesale & retail | 2021 |
| Upbeatideas UK Ltd | Administrative & support | 2014 |
| Upend Limited | Real estate | 1981 |
| Upfrica UK Ltd | Wholesale & retail | 2020 |
| Uphieght Ltd | Information & communication | 2019 |
| Upper Manor Farm Management Limited | Other services | 2005 |
| Upperwood Consultancy Limited | Information & communication | 2014 |
| Uproot Technologies Ltd | Wholesale & retail | 2022 |
| Upsilon Holdings Limited | Financial services | 2023 |
| Uptime Systems Ltd | Manufacturing | 2016 |
| Upton Grange Flats Management (NO 1) Limited | Households | 1998 |