| Toronto Management (Shortlands) Limited | Households | 2001 |
| Toroso Capital Ltd | Financial services | 2019 |
| Torquetech Mobile Ltd | Wholesale & retail | 2025 |
| Torrenueva Limited | Professional & scientific | 2016 |
| Tosal Services Ltd | Administrative & support | 2025 |
| Tosin Consultants Limited | Wholesale & retail | 2014 |
| Total Fire Solutions (London) Ltd | Professional & scientific | 2024 |
| Total Glass Solutions (London) Ltd | Construction | 2022 |
| Total Glass Solutions and Windows Ltd | Construction | 2022 |
| Total Glass Solutions Ltd | Construction | 2007 |
| Totally Drained Ltd | Water & waste | 2019 |
| Tottos Properties 2 Limited | Real estate | 2025 |
| Tottos Properties Limited | Real estate | 2024 |
| Touchfood Productions Limited | Information & communication | 2014 |
| Touchline Promotions Ltd | Hospitality | 2024 |
| Tower Mill Place Limited | Households | 2026 |
| Tower Wharf Freehold Limited | Households | 2015 |
| Town Stay Management Ltd | Real estate | 2026 |
| Towne Property Ltd | Real estate | 2020 |
| Townley Office Equipment Limited | Wholesale & retail | 1975 |
| Toyar Ltd | Health & social care | 2018 |
| TP Consultant Services Ltd | Professional & scientific | 2018 |
| TP International Legal Services Ltd | Professional & scientific | 2020 |
| Tracas Service Limited | Other services | 2012 |
| Tracvantage (UK) Limited | Wholesale & retail | 2024 |
| Trade Delivery Centre Limited | Transport & logistics | 2024 |
| Trade Services Associates UK Limited | Construction | 1993 |
| Trade to Developer Ltd | Education | 2024 |
| Tradeinbox Limited | Other services | 2017 |
| Tradermade Systems Ltd | Information & communication | 2012 |
| Tradesperson Solutions Ltd | Construction | 2025 |
| Tradventures Ltd | Real estate | 2016 |
| Tradyco Ltd | Construction | 2023 |
| TRAIN4EXCELLENCE Limited | Financial services | 2019 |
| Traininghub Events Limited | Information & communication | 2010 |
| Transatlanticists Ltd | Administrative & support | 2024 |
| Transcendence Ltd | Information & communication | 2017 |
| Transcolour Limited | Professional & scientific | 1981 |
| Transform Edge Consulting Ltd | Professional & scientific | 2024 |
| Transform Edge Properties Ltd | Real estate | 2024 |
| Transformer Media Research Ltd | Information & communication | 2021 |
| Translucence Care Ltd. | Health & social care | 2016 |
| Transport Solution Holdings Ltd | Transport & logistics | 2025 |
| Travel & Property Limited | Real estate | 2010 |
| Travel & Tourism Marketing Limited | Other services | 1999 |
| Travel Concept Europe Limited | Administrative & support | 2006 |
| Travel Lynx Ltd | Extraterritorial | 2009 |
| Travelya Ltd | Transport & logistics | 2024 |
| TRE Holdings Ltd | Financial services | 2021 |
| TRE Investments Ltd | Real estate | 2021 |
| TRE Management Ltd | Real estate | 2021 |
| TRE Reliance Ltd | Real estate | 2022 |
| Trecs & Co Limited | Construction | 2003 |
| Tredegar House (Investors) Limited | Financial services | 2019 |
| Tredegar House Management Company Limited | Households | 1998 |
| Treduss Corporation Limited | Professional & scientific | 2013 |
| Trees & People Ltd | Professional & scientific | 2026 |
| Tresrelion Ltd | Wholesale & retail | 2023 |
| Trhservices Limited | Construction | 2025 |
| Tribelle Ltd | Health & social care | 2024 |
| Triceps Data Processing Limited | Information & communication | 1986 |
| Trichem (South) Limited | Wholesale & retail | 1986 |
| Trillion Planets One Ltd | Information & communication | 2025 |
| Triloyalty Marketing Solutions Limited | Professional & scientific | 2017 |
| Trimode Limited | Real estate | 1983 |
| Trina Smith Ltd | Administrative & support | 2020 |
| Tring Property Management Limited | Real estate | 2026 |
| Trinity Factors Limited | Real estate | 1995 |
| Trinity Maroney Ltd | Wholesale & retail | 2025 |
| Trinity Mews RTM Company Limited | Households | 2013 |
| Triple A-Star Leasing Limited | Real estate | 2024 |
| Triple O'S Solutions Limited | Wholesale & retail | 2023 |
| Triple Scoop Manufacturing Limited | Manufacturing | 2026 |
| Tripntravel Private Ltd | Administrative & support | 2025 |
| Tripp Sales and Marketing Ltd | Wholesale & retail | 2024 |
| Triumph Foodservice Limited | Wholesale & retail | 2014 |
| TRIX2THEMAX Fitness Limited | Arts & recreation | 2003 |
| TRJ Trading Limited | Financial services | 2013 |
| Trout Road Management Company Limited | Households | 2011 |
| Tru-Community Group Limited | Education | 2024 |
| Tru-Learn Ltd | Education | 2019 |
| True Fusion Ltd | Administrative & support | 2017 |
| True Lets Ltd | Hospitality | 1999 |
| True Method Limited | Administrative & support | 2014 |
| True North 171 Limited | Professional & scientific | 2022 |
| True Path Ltd | Wholesale & retail | 2021 |
| True Players LAB Ltd | Other services | 2026 |
| True Value Tech Limited | Information & communication | 2025 |
| Truefaithhb Ltd | Wholesale & retail | 2025 |
| Truefit Training Limited | Arts & recreation | 2011 |
| Truepenny’S Ltd | Professional & scientific | 2024 |
| Trulyfresh Ltd | Manufacturing | 2026 |
| Trussler Consultants Ltd | Professional & scientific | 2020 |
| Trust Payments Ltd | Professional & scientific | 2019 |
| Trusted Leaflet Distribution Team Ltd | Transport & logistics | 2017 |
| Trustspark Limited | Construction | 2019 |
| Truststone Construction Limited | Construction | 2024 |
| Trusty Pack Global Ltd | Wholesale & retail | 2024 |
| Trutview Limited | Administrative & support | 2000 |
| TSB Services Limited | Professional & scientific | 2018 |