| Trinity Trailers Limited | Transport & logistics | 2023 |
| Triple Crown Consulting Ltd | Professional & scientific | 2022 |
| Triplec Electrical Maintenance Limited | Construction | 2015 |
| Trojan-Mek Limited | Manufacturing | 2004 |
| Tru-Property Limited | Real estate | 2019 |
| Truck Sale Enterprises Ltd | Wholesale & retail | 2015 |
| Truckman Bridgend Limited | Administrative & support | 2025 |
| True North PMM Ltd | Administrative & support | 2024 |
| Truplate Limited | Manufacturing | 1997 |
| Trydan Training Ltd | Construction | 2017 |
| TSF Property Solutions Limited | Real estate | 2022 |
| TSW Management Limited | Other services | 2011 |
| TSW Management Solutions Ltd | Extraterritorial | 2009 |
| TSW Training Limited | Education | 2007 |
| TTN OHA Ltd | Health & social care | 2022 |
| Turberville Properties Ltd | Real estate | 2021 |
| Turner & Morgan Developments Ltd | Construction | 2022 |
| Turner Key Properties Ltd | Real estate | 2025 |
| Turners Plum and Heat Limited | Construction | 2025 |
| Turquoise Metropolis Ltd. | Real estate | 2018 |
| Tuska Training Ltd | Education | 2023 |
| Tusow Limited | Professional & scientific | 2017 |
| TUT Auto Repairs Limited | Wholesale & retail | 2021 |
| Tuxbet Ltd | Information & communication | 2019 |
| Twcc Ltd | Manufacturing | 2011 |
| Twelfth Letting Ltd | Real estate | 2022 |
| Twibli Limited | Financial services | 2017 |
| TWIST2PAY Limited | Information & communication | 2020 |
| TY Bryn Properties Ltd | Real estate | 2019 |
| TY Caredig Supported Living Limited | Health & social care | 2022 |
| TY Coffi Ltd | Hospitality | 2025 |
| TY Collective Ltd | Real estate | 2026 |
| TY Cysgu Limited | Health & social care | 2013 |
| TY Eledi Ltd | Real estate | 2020 |
| TY Gwenyn Ltd | Health & social care | 2026 |
| TY Newydd Properties Limited | Hospitality | 2013 |
| TY Newydd Property Developments Limited | Real estate | 2025 |
| TY Sant Management Company Limited | Extraterritorial | 2009 |
| TY Tanglwyst Dairy Limited | Manufacturing | 2007 |
| Ty-Mar Domestic Services Ltd | Administrative & support | 2024 |
| Ty-Nant Electrical Services Ltd | Construction | 2006 |
| Tybio Limited | Professional & scientific | 2012 |
| Tydraw Properties (Bridgend) Ltd | Real estate | 2021 |
| Tymaen Fish and Chips Ltd | Hospitality | 2025 |
| Tymedia Limited | Professional & scientific | 2020 |
| Tynest Ltd | Real estate | 2025 |
| Tyrone Hicks Transport Ltd | Transport & logistics | 2003 |
| Tyrone Joshua Owen Limited | Extraterritorial | 2023 |
| Tythegston Green Ventures Limited | Real estate | 2010 |
| Tythegston Properties Limited | Extraterritorial | 1989 |
| TZB Logistic Ltd | Transport & logistics | 2022 |
| TZE Supply Ltd | Wholesale & retail | 2026 |
| U Plastics Limited | Wholesale & retail | 2004 |
| U.K. GAS Limited | Mining & quarrying | 1991 |
| U.K. Methane Limited | Mining & quarrying | 1997 |
| Uglobal Technology Co., Ltd | Wholesale & retail | 2023 |
| UGV Drones Limited | Financial services | 2022 |
| UK Bargain Supplies Ltd | Wholesale & retail | 2023 |
| UK Digital Solutions Limited | Information & communication | 2000 |
| UK Onshore GAS Limited | Mining & quarrying | 1995 |
| UK Water Supplies Limited | Professional & scientific | 1997 |
| UK Wind Energy Limited | Energy | 1991 |
| Ultima Finance Ltd | Administrative & support | 2025 |
| Ultimate IES Limited | Construction | 2012 |
| Under Kanvas CIC | Hospitality | 2020 |
| Uni-Vent Norway Limited | Extraterritorial | 2010 |
| Unicom Telephonic Limited | | 1998 |
| UNIFORM2GO Limited | Wholesale & retail | 2008 |
| Union Foundation | Education | 1986 |
| Unique Gifting UK Limited | Wholesale & retail | 2013 |
| Unique Woodwork Limited | Manufacturing | 2020 |
| Uniqueorn Hotel Limited | Hospitality | 2017 |
| Unisan Limited | Administrative & support | 2020 |
| Unisort Holdings Limited | Financial services | 2024 |
| Unisort Ltd | Administrative & support | 2002 |
| Unit Drive Cardiff Ltd | Transport & logistics | 2019 |
| United Commercial Investments Limited | Real estate | 2015 |
| United Graphic Design Ltd | Other services | 2011 |
| United Office Products (UK) Limited | Professional & scientific | 2008 |
| United Worldwide Distribution Ltd | Transport & logistics | 2020 |
| United Worldwide Logistics Limited | Transport & logistics | 2007 |
| Unity Accountancy Ltd | Professional & scientific | 2022 |
| Unity Accountancy SPV1 Ltd | Professional & scientific | 2022 |
| Unity Accountancy SPV2 Limited | Professional & scientific | 2023 |
| Universal Academy of the Arts Ltd | Arts & recreation | 2018 |
| Unleash IT Limited | Information & communication | 2010 |
| Unmanned Ground Vehicles UGV Limited | Construction | 2022 |
| Untitled Memories Limited | Information & communication | 2013 |
| UP for Grabz Property Sourcing Ltd | Real estate | 2023 |
| Upgrade Your Mindset Limited | Extraterritorial | 2023 |
| Upland Property Group Ltd | Real estate | 2024 |
| Upstream Studios Limited | Information & communication | 2025 |
| Urban Renova Ltd | Real estate | 2025 |
| UWL North Ltd | Transport & logistics | 2024 |
| UWL UK Ltd | Transport & logistics | 2017 |
| V-Mana Ltd | Manufacturing | 2023 |
| V-Trak Ltd | Manufacturing | 1996 |
| V.I.P Luxury Travel Limited | Transport & logistics | 2017 |
| Valann Limited | Hospitality | 2022 |
| Vale and Valley Developments Ltd | Construction | 2021 |