| Total Assistance Property Limited | Real estate | 2024 |
| Total Combustion Services Limited | Construction | 1995 |
| Total Financial Planning Limited | Financial services | 1998 |
| Total Utilities Cover Ltd | Other services | 2020 |
| Toucan Heating & Plumbing Limited | Construction | 2013 |
| TPM Consultancy Services Limited | Real estate | 2015 |
| TPM Roofing Contractors Limited | Construction | 2025 |
| Trace Health Ltd | Professional & scientific | 2025 |
| Trace Plumbing & Heating Limited | Construction | 2017 |
| Tracenow UK Limited | Wholesale & retail | 2022 |
| Track & Build Limited | Construction | 2011 |
| Trade Gateway Limited | Wholesale & retail | 2006 |
| Trade Link Network Ltd | Information & communication | 2026 |
| Tradeteam Services UK Limited | Construction | 2018 |
| Tradingoil International Limited | Professional & scientific | 2026 |
| Traffic Surveys UK Ltd | Professional & scientific | 2008 |
| Trans Gp&St Group Limited | Transport & logistics | 2018 |
| Transliving International | Other services | 1999 |
| Travis Tour Services LLP | | 2015 |
| Traxton Limited | Financial services | 2016 |
| Tree Tops Arborist Limited | Agriculture & fishing | 2026 |
| Treehouse Property Services Limited | Real estate | 2016 |
| Trekscape Media Ltd | Professional & scientific | 2024 |
| Trent Nominees Ltd. | Administrative & support | 1997 |
| Trevor Smith Surveys Limited | Professional & scientific | 2013 |
| Trevor Spurgeon TIR Limited | Wholesale & retail | 1997 |
| Trichromic LLP | | 2006 |
| Tridini Ltd | Extraterritorial | 2014 |
| Triflow Services Ltd | Construction | 2025 |
| Trinity Construction Services Limited | Construction | 1992 |
| Trinity Employee Ownership Trust Ltd | Other services | 2019 |
| Trinovantes Properties Limited | Construction | 1990 |
| TRIPLE7CARS Ltd | Transport & logistics | 2024 |
| Triplex Traffic Management Limited | Financial services | 2012 |
| Troop Environmental Services Ltd | Construction | 2021 |
| Trubau Engineering Survey Ltd | Construction | 2024 |
| True Tribe Ltd | Health & social care | 2024 |
| Trueblue Historic Motorworks Limited | Wholesale & retail | 2025 |
| Truemedic Ltd | Education | 2022 |
| Tryndehayes Limited | Information & communication | 2011 |
| TT Promotions Limited | Arts & recreation | 2006 |
| TTH London Limited | Administrative & support | 2024 |
| Tucker and Co London Ltd | Wholesale & retail | 2023 |
| Tudor Lodge Luxury Boarding Kennels & Cattery Limited | Agriculture & fishing | 2007 |
| Tukos Services Limited | Administrative & support | 2016 |
| Tulip Garden Design Ltd | Administrative & support | 2010 |
| Turbo Brain Limited | Real estate | 2018 |
| Turbo Charged Competitions Limited | Wholesale & retail | 2023 |
| Turbo Rendering Limited | Construction | 2022 |
| Turck Banner Limited | Wholesale & retail | 1990 |
| Turner Marke International Limited | Administrative & support | 2007 |
| Turner Songs Limited | Information & communication | 2006 |
| Turpin Properties Ltd | Real estate | 2023 |
| Tuscan Management Solutions Limited | Administrative & support | 2007 |
| Tutela Support Ltd | Health & social care | 2017 |
| Twenty-Twenty (Clothing) Limited | Manufacturing | 1986 |
| Twisters Community Gymnastics Ltd | Arts & recreation | 2018 |
| TWS Scaffolding Limited | Construction | 2018 |
| TWS Thinkwise Solutions Limited | Professional & scientific | 2017 |
| Twydell Property Limited | Real estate | 2024 |
| Tyrells Management Company Limited | Real estate | 2022 |
| TYRES24/7 Limited | Manufacturing | 2025 |
| U Store - 24-7.CO.UK Ltd | Administrative & support | 2020 |
| UAM Consult Limited | Construction | 2015 |
| UBN Trading Limited | Wholesale & retail | 2023 |
| UK Commissioning Ltd | Manufacturing | 2014 |
| UK Cube Association CIC | Arts & recreation | 2023 |
| UK First Choice Property Solutions Limited | Construction | 2026 |
| UK Makeup & Aesthetics Ltd | Other services | 2021 |
| UK Measures Limited | Transport & logistics | 2016 |
| UK Picture Editors Guild Awards Ltd | Administrative & support | 2010 |
| Ukcb Limited | Wholesale & retail | 2023 |
| Ultimate Fishing Limited | Administrative & support | 2024 |
| Ultimate Pool Coaching Limited | Administrative & support | 2024 |
| Ultimate Pool Group Limited | Administrative & support | 2020 |
| Ultimate Pool Rentals Limited | Administrative & support | 2025 |
| Ultimate Pool Retail Limited | Administrative & support | 2025 |
| Ultimate Sealants Limited | Construction | 2024 |
| Ultra Spark Classic Ignition Limited | Wholesale & retail | 2025 |
| UNA Jones Limited | Other services | 2021 |
| Unbelievable Media Ltd | Wholesale & retail | 2025 |
| Undisputed Autos Ltd | Wholesale & retail | 2026 |
| Unge Sky Property Ventures Ltd | Real estate | 2022 |
| UNI Consultancy Limited | Information & communication | 2020 |
| Unijovic Care Ltd | Health & social care | 2025 |
| Unique and Useful Ltd | Wholesale & retail | 2020 |
| Unique Building Solutions (Kent) Limited | Construction | 2017 |
| Unique Gymnastics Limited | Arts & recreation | 2019 |
| Unique Homes (Sussex) Ltd | Construction | 2024 |
| Unique Homes Holdings Ltd | Financial services | 2024 |
| Unit 24 Ltd | Wholesale & retail | 2025 |
| United Van Hire Essex Ltd. | Administrative & support | 2001 |
| Universal Building Specialists Ltd | Construction | 2013 |
| Universal Central Services Ltd | Administrative & support | 1997 |
| Universal Demolition Limited | Construction | 2016 |
| Universal Flags Limited | Manufacturing | 2013 |
| Universal Flooring Specialists Ltd | Construction | 2015 |
| Universal M & E Ltd. | Construction | 2015 |
| Universal Panels & Systems Limited | Manufacturing | 2007 |
| Universal Site Services Limited | Construction | 2024 |