| Trading Depot U.K. Limited | Wholesale & retail | 2007 |
| Trafford Insurance Services Limited | Financial services | 1995 |
| Train With RHI Ltd | Other services | 2022 |
| Training for Success Limited | Professional & scientific | 1997 |
| Trainingindata Limited | Education | 2022 |
| Tranquil Tots Limited | Other services | 2024 |
| Trans-Technology Consulting Limited | Information & communication | 1996 |
| Transform Finance Limited | Professional & scientific | 2012 |
| Transform Society | Other services | 2018 |
| Transilvania Events Ltd | Hospitality | 2026 |
| Travel Brit UK Limited | Administrative & support | 2024 |
| Travel Faster Limited | Administrative & support | 2025 |
| Travel Safety Limited | Administrative & support | 2016 |
| Travitalia Limited | Financial services | 1980 |
| Travpad Limited | Information & communication | 2011 |
| Treasure Forge Studio Ltd | Wholesale & retail | 2021 |
| Treasure Island Coins & Collectibles Limited | Wholesale & retail | 2025 |
| Treasure Limited | Professional & scientific | 2006 |
| Trench Ghost Media Ltd | Professional & scientific | 2025 |
| Trendy Haryana Ltd | Wholesale & retail | 2025 |
| Trevett Facilities Recruitment USA Ltd | Administrative & support | 2020 |
| Trevett Professional Services Ltd | Professional & scientific | 2015 |
| Trevor Marshall Consultancy Services Limited | Professional & scientific | 2012 |
| Trevor Taylor EXP Ltd | Real estate | 2022 |
| Treweren Services Limited | Professional & scientific | 2019 |
| Triangulate Marketing Limited | Professional & scientific | 2018 |
| Tributaries Limited | Administrative & support | 2024 |
| Trilogy Marketing Limited | Administrative & support | 1997 |
| Trimentis Limited | Professional & scientific | 2001 |
| Trimline Interiors UK Limited | Construction | 2025 |
| Trinity Controls Integrated Services Ltd | Construction | 2023 |
| Triopsis Limited | Information & communication | 2006 |
| Triple Cooked Chips Limited | Administrative & support | 2010 |
| Triple G Ltd | Professional & scientific | 2020 |
| Tripli Holdings Ltd | Financial services | 2025 |
| Trips From London Ltd | Administrative & support | 2017 |
| Trish Investments Limited | Professional & scientific | 2019 |
| Triton Interco 1 Limited | Financial services | 2026 |
| Triton Interco 2 Limited | Financial services | 2026 |
| Triton Newco 1 Limited | Financial services | 2023 |
| Triton Newco 2 Limited | Financial services | 2023 |
| Triton UK Midco Limited | Financial services | 2018 |
| Triveni 98 Limited | Professional & scientific | 2015 |
| TRP Creative Ltd | Information & communication | 2026 |
| Truckmar Ltd | Transport & logistics | 2019 |
| True Fresh Cleaning Limited | Administrative & support | 2026 |
| Truefans Technologies Limited | Wholesale & retail | 2025 |
| Truepath Commerce Ltd | Wholesale & retail | 2023 |
| Trumanco Limited | Other services | 2018 |
| Trust Motor Transport Ltd | Wholesale & retail | 2021 |
| Trusted Retail & Outlet Limited | Professional & scientific | 2019 |
| Trustee and Pension Management Training and Publishing Limited | Education | 2005 |
| TSJ Property Holdings Limited | Real estate | 2021 |
| Tsrm Consulting Ltd | Wholesale & retail | 2017 |
| Tsumiki Ltd | Professional & scientific | 2011 |
| TT Werkhoven Limited | Other services | 2013 |
| Tuba Goodness Ltd | Information & communication | 2020 |
| Tubogel (UK) Ltd | Manufacturing | 2018 |
| Tudor Barn Weddings Ltd | Hospitality | 2014 |
| Tulip Court Management Company Limited | Real estate | 1973 |
| Tungsten Bidco Limited | Financial services | 2019 |
| Tunnel Cement Limited | Financial services | 1975 |
| Turnbull Associates Slough Limited | Professional & scientific | 1996 |
| Turqle UK Ltd | Wholesale & retail | 2018 |
| Tussilago Limited | Information & communication | 2015 |
| TVC4 Limited | Professional & scientific | 2015 |
| TVI 1 Limited | Professional & scientific | 2013 |
| TVI Compliance Limited | Administrative & support | 2023 |
| TVI Distribution Ltd | Wholesale & retail | 2015 |
| TVI Group Limited | Professional & scientific | 2014 |
| TVI Investors Club Limited | Professional & scientific | 2026 |
| TVI Manufacturing Ltd | Professional & scientific | 2014 |
| Tvibiz Limited | Professional & scientific | 2000 |
| Tvig Limited | Financial services | 2017 |
| TW Securities Limited | Administrative & support | 2022 |
| Twdf Holdings Limited | Information & communication | 2020 |
| Twdf Mini ME Limited | Information & communication | 2020 |
| Twentyfivefurther Limited | Information & communication | 2024 |
| TWF Group Productions Ltd | Information & communication | 2026 |
| Twinkle Totz Ltd | Education | 2025 |
| Twistdx Limited | Professional & scientific | 2002 |
| Two Chics Media Ltd | Information & communication | 2021 |
| Twyford Tractors Ltd | Manufacturing | 2025 |
| Tyne Waste Ltd | Water & waste | 1992 |
| Tyreco Waste Services Limited | Water & waste | 2025 |
| Tyres & Wheels Direct Limited | Professional & scientific | 1992 |
| Tyres Direct Limited | Wholesale & retail | 1991 |
| Tyrian UK Limited | Real estate | 2008 |
| Tyrone Lebon Studio Ltd | Professional & scientific | 2018 |
| Tyzer Film Services Ltd | Information & communication | 2017 |
| U & I Fuels Limited | Wholesale & retail | 2007 |
| U SAY Limited | Information & communication | 2019 |
| U Want Cars Limited | Transport & logistics | 2012 |
| U Want Limited | Transport & logistics | 2012 |
| U Want Private Hire Limited | Transport & logistics | 2012 |
| U-Want Taxis Limited | Extraterritorial | 1993 |
| U.K. Tyres (West London) Limited | Wholesale & retail | 2017 |
| Uber Cool Ltd | Construction | 2021 |
| Uberz Taxi Ltd | Transport & logistics | 2019 |
| Ubidy Ltd | Administrative & support | 2017 |