| Traktrux Limited | Wholesale & retail | 1980 |
| Tramforward Limited | Extraterritorial | 2018 |
| Tramline Media Ltd | Information & communication | 2025 |
| Tran's Food Limited | Manufacturing | 1995 |
| Tran's Properties Ltd | Real estate | 2019 |
| Trance Central Peterborough Limited | Arts & recreation | 2025 |
| Tranquil Touch Limited | Health & social care | 2021 |
| Tranquilidade Ltd | Health & social care | 2025 |
| Tranquility Lakes Ltd | Real estate | 2026 |
| Trans AM Ltd | Transport & logistics | 2016 |
| Trans DUD Limited | Transport & logistics | 2017 |
| Trans Kris Limited | Administrative & support | 2014 |
| Trans Kristof Ltd. | Transport & logistics | 2016 |
| Trans Krzys Limited | Transport & logistics | 2020 |
| Trans Mark 74 Ltd | Transport & logistics | 2019 |
| Transbreak Limited | Households | 1997 |
| Transease Ltd | Transport & logistics | 2018 |
| Transforge (U.K.) Limited | Manufacturing | 1990 |
| Transformation Analytics Limited | Information & communication | 2009 |
| Transformation Consultancy Ltd | Information & communication | 2025 |
| Transformational Therapies Limited | Health & social care | 2024 |
| Transformative Education Initiative UK Ltd | Education | 2019 |
| Transient Wolf Properties Limited | Real estate | 2020 |
| Transimperia Ltd | Transport & logistics | 2016 |
| Transkas Ltd | Transport & logistics | 2019 |
| Translog Ltd | Administrative & support | 2017 |
| Transparent Property Services Limited | Construction | 2010 |
| Transparent Rendering Services Limited | Construction | 2021 |
| Transport Angels Group Ltd | Transport & logistics | 2026 |
| Transport Elena Limited | Transport & logistics | 2026 |
| Transport Media Pages Limited | Manufacturing | 2019 |
| Transport Publishing Network Limited | Information & communication | 2021 |
| Transportbeat Ltd | Transport & logistics | 2024 |
| Transvision Associates Ltd | Real estate | 2025 |
| Trauma Pain Support Ltd | Education | 2025 |
| Travel 24 Seven Ltd | Administrative & support | 2023 |
| Travel Websites and Images.Com Ltd | Information & communication | 2021 |
| Travelex Agency Services Limited | Administrative & support | 2002 |
| Travelex Central Services Limited | Administrative & support | 2005 |
| Travelex Currency Services Limited | Administrative & support | 1999 |
| Travelex Europe Limited | Administrative & support | 2015 |
| Travelex Foreign Coin Services Limited | Financial services | 1994 |
| Travelinabox Ltd | Administrative & support | 2021 |
| Travelkeeperuk Ltd | Administrative & support | 2025 |
| Travellers Cheques Encashment Services Limited | Administrative & support | 2012 |
| Travellers Exchange Corporation Limited | Professional & scientific | 1998 |
| Trazport Ltd | Transport & logistics | 2025 |
| Tread and Track Ltd | Wholesale & retail | 2023 |
| Treasured Event Hire Ltd | Arts & recreation | 2024 |
| Treatix Limited | Wholesale & retail | 2025 |
| Treats Direct Limited | Wholesale & retail | 2015 |
| Tree and Landscape Specialist Ltd | Administrative & support | 2025 |
| Tree of Life Creations LLP | | 2021 |
| Tree-Vine Limited | Arts & recreation | 1997 |
| Treetunnel Ltd | Financial services | 2023 |
| Trenchard Square (Scampton) Residents Company Limited | Households | 2026 |
| Trend Ecoms Ltd | Wholesale & retail | 2025 |
| Trend Solutions UK Limited | Wholesale & retail | 2019 |
| Trendguru Ltd | Extraterritorial | 2025 |
| Trendyx Limited | Wholesale & retail | 2025 |
| Trent Logistics Ltd | Transport & logistics | 2025 |
| Tresham Motors Limited | Wholesale & retail | 2006 |
| Trevfilan Limited | Real estate | 2009 |
| Trevor Marks Gates & Automation Limited | Construction | 2019 |
| Triangle Supermarket Limited | Wholesale & retail | 2011 |
| Tribe Assets Limited | Transport & logistics | 2016 |
| Triblaz Limited | Manufacturing | 2010 |
| Tricare Body Mind and Soul Limited | Health & social care | 2014 |
| Trichocentre Limited | Extraterritorial | 2016 |
| Tricio Investment Advisors Limited | Administrative & support | 2020 |
| Tricrossland Limited | Education | 2017 |
| Trident Property Esher 01 Limited | Financial services | 2024 |
| Trika Capital LLP | | 2024 |
| Trilogy Lighting Ltd | Arts & recreation | 2023 |
| Trim Direct Ltd | Information & communication | 2025 |
| Trim Yard Limited | Other services | 2024 |
| Trinity Empire Limited | Wholesale & retail | 2025 |
| Trinity Entertainment Holdings Ltd | Information & communication | 2018 |
| Trinity Entertainment Media Limited | Arts & recreation | 2016 |
| Trinity Film & TV Ltd | Information & communication | 2014 |
| Trinity Grange (Cambridge) Management Company Limited | Households | 2006 |
| Trinity IT Services Ltd | Information & communication | 2024 |
| Trinity Trading Corporation Ltd | Extraterritorial | 2001 |
| Trio Couriers Limited | Transport & logistics | 2024 |
| Trio Enterprises Limited | Other services | 2025 |
| Triple Seven Construction & Development Limited | Real estate | 2007 |
| Triple-A IT Solutions Limited | Information & communication | 2015 |
| Triple-Ts Cuisine Ltd | Hospitality | 2025 |
| Tripmoni Technology Limited | Professional & scientific | 2023 |
| Trislon Ltd | Information & communication | 2026 |
| Tristar Global Comms Limited | Extraterritorial | 2008 |
| Tristar Global Communications Limited | Information & communication | 2005 |
| Tristar Global Developments Limited | Other services | 2018 |
| Tristar Global Facilities Management Ltd | Administrative & support | 2017 |
| Trivedi Group Ltd | Wholesale & retail | 2021 |
| Triventuresuk Ltd | Education | 2022 |
| Trmland Roadside Limited | Professional & scientific | 2023 |
| Trmw Properties Limited | Professional & scientific | 2014 |
| Trofida Ltd | Wholesale & retail | 2021 |
| Trojan Property Investment Holdings Limited | Financial services | 2019 |