| Trail to the Top Ltd | Education | 2025 |
| Train 2 Success Ltd | Education | 2021 |
| Trance Health Limited | Health & social care | 2024 |
| Tranquil Dental Ltd | Health & social care | 2024 |
| Tranquility Nail and Beauty Salon Ltd | Administrative & support | 2018 |
| Trans-Hugo Ltd | Transport & logistics | 2019 |
| Transcendence Consultants Ltd | Information & communication | 2023 |
| Transilvania Groceries Ltd | Wholesale & retail | 2024 |
| Transpiritdelights Ltd | Hospitality | 2023 |
| Transpolita Ltd | Wholesale & retail | 2015 |
| Transport Help UK. Limited | Transport & logistics | 2000 |
| Travel and Transfer Limited | Transport & logistics | 2025 |
| Travel Easy LLP | | 2016 |
| Travel Outside the Box CIC | Information & communication | 2024 |
| Travelnet Systems Ltd | Information & communication | 2010 |
| Travertine Consulting Limited | Information & communication | 2010 |
| TRC Developments Ltd | Extraterritorial | 2015 |
| TRC Meats Ltd | Wholesale & retail | 2026 |
| Treadmill Construction Limited | Professional & scientific | 2018 |
| Tree Tops (Romford) Limited | Health & social care | 2011 |
| Trefoil Technology Limited | Water & waste | 2009 |
| Treisure Ltd | Administrative & support | 2025 |
| Tremblant Technologies Ltd | Information & communication | 2016 |
| Trendhatchuk.Com Ltd | Wholesale & retail | 2025 |
| Trendy Landscapes Ltd. | Administrative & support | 2017 |
| Trent Barber Shop Ltd | Other services | 2026 |
| Trentcourt Properties Limited | Real estate | 2000 |
| Tressider Benson Limited | Professional & scientific | 2021 |
| Trevor Bolton Associates Limited | Professional & scientific | 2019 |
| Trewince Farms Limited | Financial services | 2017 |
| TRF Properties Limited | Real estate | 2003 |
| Triangle Heating Ltd | Construction | 2026 |
| Tribill Ltd | Extraterritorial | 2024 |
| Tricar Developments Ltd | Construction | 2026 |
| Tricker & Baker Limited | Financial services | 2012 |
| Trident Capital Investments Ltd | Financial services | 2026 |
| Trident Facilities Services Ltd | Administrative & support | 2002 |
| Trident Gear Ltd | Manufacturing | 2018 |
| Trident Pharma Properties Limited | Real estate | 2015 |
| Trident Wholesale Ltd | Wholesale & retail | 2018 |
| Trifactor Limited | Professional & scientific | 2023 |
| Trigon Interiors Ltd | Wholesale & retail | 2022 |
| Trikona Electrical Solutions Ltd | Construction | 2026 |
| Trilux Lighting Limited | Manufacturing | 1988 |
| Trimark Group Ltd | Construction | 2026 |
| Trimer CL Limited | Construction | 2020 |
| Trinity Service Station Holdings Ltd | Financial services | 2022 |
| Trinity Service Station Limited | Wholesale & retail | 1993 |
| Tritbot Ltd | Manufacturing | 2025 |
| Tritton Farming Partnership LLP | | 2013 |
| TRM Software Limited | Information & communication | 2024 |
| Trochilics Limited | Manufacturing | 1988 |
| Trojan Civil Engineering Limited | Construction | 2017 |
| Trojan Electrical Consultancy Limited | Professional & scientific | 2020 |
| Trojan Medical Group Limited | Health & social care | 2019 |
| Troll Treasures Ltd | Wholesale & retail | 2021 |
| Tromley Ltd | Health & social care | 2010 |
| Trotter UK Mobile Billboards Ltd | Professional & scientific | 2015 |
| Trou DE CUL Rouge Ltd | Financial services | 2020 |
| TRU FM Ltd | Transport & logistics | 2024 |
| TRU Logistics Ltd | Transport & logistics | 2022 |
| Truck & BUS Engineering Ltd | Transport & logistics | 2008 |
| Truck and BUS Maintenance Ltd | Transport & logistics | 2015 |
| Truck Paint Limited | Wholesale & retail | 2017 |
| True Arabica Coffee Limited | Manufacturing | 2026 |
| True ARM TP Ltd | Professional & scientific | 2026 |
| True Beat Music Ltd | Education | 2019 |
| True Colours Renovations Limited | Construction | 2022 |
| True Wellth Ltd | Health & social care | 2022 |
| Truedge Automotive Ltd | Wholesale & retail | 2025 |
| Truedge Stone & Ceramics Ltd | Construction | 2021 |
| Trueframe Windows and Doors Ltd | Manufacturing | 2026 |
| Trueloves Grange (Ingatestone) Management Company Limited | Households | 2015 |
| Trueloves Site Management Ltd | Households | 2017 |
| Trueshield Limited | Wholesale & retail | 2026 |
| Truman Place Management Company Limited | Households | 2025 |
| Trupoint Compliance Limited | Professional & scientific | 2023 |
| Trusko Developments Ltd | Construction | 2020 |
| Trust Surgical Limited | Health & social care | 2014 |
| Trusted Advisers (UK) Ltd | Professional & scientific | 2016 |
| Trustustocall Ltd | Information & communication | 2018 |
| TS Brickwork and Construction Ltd | Construction | 2016 |
| TS Consultancy Ltd | Professional & scientific | 2026 |
| TS3 (UK) Ltd | Information & communication | 2012 |
| TSC Clinics Ltd | Health & social care | 2025 |
| TSC Holdco Ltd | Financial services | 2024 |
| TSK Wealth Management Ltd | Households | 2019 |
| Tstl Enterprises Ltd | Agriculture & fishing | 2017 |
| TT Coaching Ltd | Arts & recreation | 2023 |
| TT Company Braintree Ltd | Other services | 2026 |
| TT Company Maldon Ltd | Other services | 2025 |
| TT Company Takeley Ltd | Other services | 2026 |
| TT Cooling Limited | Construction | 2024 |
| TT Fitness Limited | Wholesale & retail | 2019 |
| TTB Property Investment Ltd | Real estate | 2025 |
| TTC Wetranslate Limited | Professional & scientific | 1997 |
| TTV Investments Limited | Real estate | 2020 |
| Tucker GAS Limited | Construction | 2015 |
| Tuden Property Investments Company Limited | Real estate | 2025 |
| Tugela People Ltd | Professional & scientific | 2009 |