| Tredici Rustico Limited | Hospitality | 2019 |
| Treehouse Cafe and Ices Ltd | Hospitality | 2026 |
| Trellis Lane Trading Ltd | Wholesale & retail | 2026 |
| Trendy-Street UK Ventures Ltd | Other services | 2026 |
| Tri-Pack Packaging Systems Limited | Manufacturing | 1973 |
| Tribal 24 Online LLP | | 2011 |
| Tricrest Homes Limited | Administrative & support | 1998 |
| Trifa Health Ltd | Health & social care | 2025 |
| Trilock Supplies (UK) Limited | Construction | 2018 |
| Trimco Ltd | Other services | 2018 |
| Trimodus Ltd | Information & communication | 2005 |
| Tristar Consulting Limited | Professional & scientific | 2006 |
| Tronox Holdings PLC | Financial services | 2018 |
| Tronox Investment Holdings Limited | Financial services | 2019 |
| Tronox Investments UK Limited | Professional & scientific | 2011 |
| Tronox Pigment UK Limited | Manufacturing | 1920 |
| Tronox UK Holdings Limited | Financial services | 2016 |
| Tronox UK Merger Company Limited | Financial services | 2018 |
| Truck Clinic Ltd | Manufacturing | 2023 |
| Truck Stop Pizza Limited | Hospitality | 2025 |
| True Artists Ltd | Arts & recreation | 2018 |
| True Tech Training Ltd | Education | 2016 |
| Truefix Ceilings Limited | Construction | 2002 |
| Truly Scrumptious (Lincs) Limited | Wholesale & retail | 2016 |
| Truscote Grange Management Company Limited | Households | 2009 |
| Trust Advice Solutions CIC | Other services | 2012 |
| Trusted Tuition Ltd | Education | 2025 |
| Trypp Limited | Information & communication | 2020 |
| TSB Limited | Construction | 2017 |
| TSL Consultancy Services (Lincs) Ltd | Professional & scientific | 2021 |
| TSW Roofing Ltd | Construction | 2025 |
| Ttobba Tech Limited | Wholesale & retail | 2019 |
| TTT Beauty Ltd | Other services | 2024 |
| Tucker Medical Services Ltd | Health & social care | 2015 |
| Tudor Homes (Anglia) Limited | Construction | 1927 |
| Tura Driving Ltd | Transport & logistics | 2019 |
| Turned Parts Limited | Manufacturing | 2011 |
| Turner Evans Stevens (Holdings) Limited | Real estate | 2002 |
| Turners Precision Machining Services Ltd | Manufacturing | 2024 |
| Tutty Road Transport Limited | Transport & logistics | 2010 |
| TV Business Development Ltd | Extraterritorial | 2010 |
| TVS Lincolnshire Ltd | Health & social care | 2022 |
| Twelve Talent Ltd | Administrative & support | 2015 |
| Twin Housing Ltd | Real estate | 2025 |
| Twist & Flip Gymnastics | Arts & recreation | 2022 |
| Two Reasons WHY Ltd | Financial services | 2016 |
| Twyford Art Supplies Ltd | Professional & scientific | 2013 |
| TXR Properties Ltd | Other services | 2015 |
| Tyas (Joinery & Building) Ltd | Construction | 2008 |
| Tyfab Ltd | Professional & scientific | 2019 |
| Tygo Retail Ltd | Wholesale & retail | 2021 |
| Tyler Properties (Grimsby) Limited | Real estate | 2004 |
| Tyrer Creative Ltd | Administrative & support | 2019 |
| Tyrestop Limited | Wholesale & retail | 2020 |
| Tyson Close Developments Ltd | Construction | 2022 |
| U.K. Container Repairs Ltd | Manufacturing | 2016 |
| U.K. Trading Partnership Ltd | Wholesale & retail | 2011 |
| Uafn Communications Ltd | Information & communication | 2021 |
| Uafn Group Ltd | Financial services | 2026 |
| Udhelogho Limited | Health & social care | 2019 |
| UK Fire Protection & Maintenance Services Ltd | Manufacturing | 2019 |
| UK Grid Investments Limited | Professional & scientific | 2013 |
| UK Quality Brand Ltd | Hospitality | 2025 |
| UK Safety Netting Services Limited | Construction | 2015 |
| UK Scaffold & Building Supplies Ltd | Wholesale & retail | 2018 |
| UK Seafood Federation Limited | Other services | 2024 |
| UK Stocked Asset Management Limited | Households | 2012 |
| UK Trailer Parts Limited | Manufacturing | 2009 |
| UK Vehicle Data Limited | Information & communication | 2015 |
| UK Wash Ltd | Transport & logistics | 2025 |
| UK Webworks Ltd | Professional & scientific | 2024 |
| UK4TRANSPORT Ltd | Transport & logistics | 2024 |
| UKN Parking Limited | Other services | 2025 |
| Ukrainian Culture Hub Ltd | Education | 2025 |
| UKT Holdings Ltd | Real estate | 2021 |
| Ulph & Kearns Limited | Health & social care | 2009 |
| Ultimate Autos Ltd | Wholesale & retail | 2018 |
| Ultimate Electrical Group Limited | Construction | 2026 |
| Ultimate Fire & Security Limited | Construction | 2026 |
| Ultimate Group Ventures Ltd | Wholesale & retail | 2026 |
| Ultimate Mechanical Services Limited | Construction | 2026 |
| Ultimate One Electrical Ltd | Construction | 2015 |
| Ultra Pure UK Limited | Wholesale & retail | 2026 |
| Ultrasonic Cleaning Company Limited | Manufacturing | 2011 |
| Ultratherm Site Services Limited | Construction | 2025 |
| Umios Food UK Limited | Wholesale & retail | 2000 |
| Umojah Barbers Ltd | Other services | 2020 |
| Under Pressure JET Washing and Gutter Cleaning Ltd | Administrative & support | 2025 |
| Underpin Nutrition Ltd | Education | 2022 |
| Underwood Developments Limited | Construction | 2015 |
| Unibuild Building Contractors Limited | Construction | 1999 |
| Unibuild Holdings Ltd | Financial services | 2021 |
| Unicorn Healthcare Services Ltd | Health & social care | 2022 |
| Unified (UK) Limited | Hospitality | 2015 |
| Union Richmond Ltd | Construction | 2019 |
| Unit One Club Ltd | Other services | 2021 |
| United Autoparts Limited | Wholesale & retail | 2004 |
| United European Car Carriers (Grimsby) Limited | Transport & logistics | 1992 |
| United Group Developments Ltd | Real estate | 2023 |
| Unityspacehousing Ltd | Professional & scientific | 2026 |