| TWL Irrigation Limited | Manufacturing | 2008 |
| Two Faced Twins Limited | Arts & recreation | 2020 |
| Two Kats and a COW Gallery Limited | Wholesale & retail | 2014 |
| Two Thirds Blue Limited | Administrative & support | 2016 |
| Two Three Music Limited | Arts & recreation | 2023 |
| Two Way Productions Limited | Extraterritorial | 2013 |
| TWR Enterprises Limited | Information & communication | 2016 |
| TWR Homes Limited | Real estate | 2019 |
| TXM Limited | Health & social care | 2017 |
| Tyche Management Services Limited | Professional & scientific | 2023 |
| Tyrese Property Investments Ltd | Real estate | 2025 |
| Tyrese T Properties Ltd | Real estate | 2025 |
| TZ250 Limited | Wholesale & retail | 2015 |
| U2 Consultancy Ltd | Other services | 2014 |
| U2 Developments Holdings Ltd | Households | 2022 |
| U2 Developments Ltd | Real estate | 2019 |
| Ugly Duck Design & Animation Ltd | Professional & scientific | 2020 |
| UK Facilities Support Limited | Administrative & support | 2023 |
| UK Financial Literacy Foundation | Other services | 2022 |
| UK Flyers Ltd | Extraterritorial | 2001 |
| UK Healthcare Group Limited | Health & social care | 2004 |
| UK International Healthcare Management Association Limited | Health & social care | 2017 |
| UK Photo Tours Ltd | Administrative & support | 2025 |
| UK Pick and Pack Limited | Extraterritorial | 2013 |
| UK Stock-Sell Trading Ltd | Wholesale & retail | 2025 |
| UK Top Barbers Z Ltd | Other services | 2025 |
| UK Trading Partners Limited | Administrative & support | 2013 |
| UK Vine Care Limited | Agriculture & fishing | 2014 |
| Ukaan | Education | 2015 |
| Ukap (UK Adhd Partnership) | Education | 2013 |
| UKH2O Limited | Administrative & support | 2010 |
| Ukhb Ltd | Real estate | 2010 |
| Ukhelix Company Limited | Wholesale & retail | 2017 |
| Uksk Limited | Wholesale & retail | 2010 |
| Uksolix Limited | Wholesale & retail | 2023 |
| Ulliott Patten Financial Planning Limited | Financial services | 2025 |
| Ultimate Build (Southern) Ltd | Construction | 2019 |
| Ultimate Campers Limited | Administrative & support | 2016 |
| Ultimate Surfaces Ltd | Construction | 2022 |
| Ultimate Technologies Limited | Information & communication | 2001 |
| Ultimate U Fitness Ltd | Education | 2013 |
| Ultra Drive Ltd | Wholesale & retail | 2023 |
| Ulya Foods Ltd | Wholesale & retail | 2021 |
| Umbra International Limited | Other services | 2021 |
| UMI Clinics Ltd | Health & social care | 2023 |
| Uncle Sams Broadwater Ltd | Hospitality | 2024 |
| Under Influence Ltd | Information & communication | 2024 |
| Under One Cloud Consultancy Ltd | Other services | 2019 |
| Under the Radar FC Limited | Arts & recreation | 2023 |
| Underdog Strength Ltd | Arts & recreation | 2022 |
| Understanding Sport Ltd | Manufacturing | 2021 |
| Uniclean Property Maintenance Limited | Administrative & support | 2002 |
| Unicorn Direct Limited | Transport & logistics | 2016 |
| Unicorn Removals Ltd | Extraterritorial | 2006 |
| Uniform Girls Ltd | Wholesale & retail | 2024 |
| Unify Digital Limited | Information & communication | 2024 |
| Union Jack Property Limited | Real estate | 2013 |
| Unique Hairdresser Worthing Ltd | Other services | 2023 |
| Unique Sussex Property Limited | Real estate | 2021 |
| Uniquely YOU Ltd | Other services | 2010 |
| Uniscan Limited | Manufacturing | 1983 |
| Unit 316 Ltd | Manufacturing | 2026 |
| Unite Information Technology Ltd | Administrative & support | 2022 |
| United Expat Ltd | Information & communication | 2018 |
| United Foster Carers Association | Health & social care | 2004 |
| United Magic Limited | Information & communication | 2010 |
| Unitissue Limited | Wholesale & retail | 1994 |
| Unity Insights Limited | Health & social care | 2021 |
| Univa Health Ltd | Public administration | 2024 |
| Universal Safety Practitioners Ltd | Professional & scientific | 2014 |
| Universal Vizyon Ltd | Education | 2025 |
| Unknown Media Ltd | Professional & scientific | 2014 |
| Unleashed Dog Day Care Ltd | Wholesale & retail | 2011 |
| Unmasked Learning Academy Ltd | Education | 2025 |
| Unthinkable Productions Limited | Information & communication | 2017 |
| UOC IOT Ltd | Information & communication | 2023 |
| UP Digital Media Ltd | Professional & scientific | 2018 |
| Upgrade Bikes Limited | Wholesale & retail | 2002 |
| Upgrade Group Limited | Financial services | 2020 |
| Upper Brighton Road 1963 Limited | Extraterritorial | 2014 |
| Upperton Vineyards Limited | Agriculture & fishing | 2016 |
| Upside VC Limited | Other services | 2023 |
| Uramaya Holdings Limited | Financial services | 2024 |
| Urban Garden Rooms Ltd | Construction | 2019 |
| Urban Greenery Ltd | Administrative & support | 2017 |
| Urban Nest Housing Solutions Community Interest Company | Hospitality | 2023 |
| Urban Regen Chelmsford Ltd | Construction | 2024 |
| Urban Regen Group Ltd | Construction | 2024 |
| Urban Regen International Ltd | Construction | 2024 |
| Urban Regen Kingsway Ltd | Construction | 2024 |
| Urban Regen Shoreham Ltd | Construction | 2024 |
| Urban Regen Southgate Ltd | Construction | 2024 |
| Urban Roost Ltd | Hospitality | 2024 |
| Urban Tadka Ltd | Hospitality | 2025 |
| Urology SK Limited | Administrative & support | 2023 |
| Usersound Ltd | Information & communication | 2025 |
| Ussk Ltd | Wholesale & retail | 2025 |
| Utility LAB Limited | Professional & scientific | 2024 |
| UTM Building Services Limited | Construction | 2011 |
| UWA Holdings Ltd | Wholesale & retail | 2023 |