| TAI TAM Estates Ltd | Real estate | 2020 |
| Taipan Limited | Financial services | 2016 |
| Taizie Ltd | Real estate | 2021 |
| Take One Services Ltd. | Information & communication | 2023 |
| Tansley Witt Limited | Households | 2017 |
| Tayleigh Limited | Real estate | 1983 |
| Taylors Asia Limited | Real estate | 2019 |
| Taylors Direct Limited | Real estate | 2000 |
| Taylors London Limited | Real estate | 2019 |
| Tcra Limited | Administrative & support | 2010 |
| Teamtogs Limited | Manufacturing | 2003 |
| Tech Pros Mobile Repair Ltd | Wholesale & retail | 2025 |
| Tending UK Ltd | Information & communication | 2026 |
| Tfgmi Services Limited | Professional & scientific | 2009 |
| TH Dwelling Ltd | Real estate | 2024 |
| Thai Paya Food Ltd | Hospitality | 2026 |
| Thai Radlett Cuisine Ltd | Hospitality | 2025 |
| Thamesown Properties Limited | Construction | 1989 |
| That Bluebird Ltd | Real estate | 2018 |
| Thavas Property Limited | Real estate | 2019 |
| THE Acquisition Finder Limited | Administrative & support | 2024 |
| THE Acquisition Group Ltd | Real estate | 2020 |
| THE Association of Registered Trichologists Limited | Other services | 2024 |
| THE BAD COP Ltd | Information & communication | 2022 |
| THE Bonds Group of Companies Limited | Professional & scientific | 1952 |
| THE Booty Boot Camp Ltd | Arts & recreation | 2017 |
| THE Chiltern Oncology Practice Ltd | Health & social care | 2012 |
| THE Communications Consultancy Ltd | Professional & scientific | 2018 |
| THE Couch Spuds Limited | Information & communication | 2013 |
| THE CUB House Limited | Other services | 2024 |
| THE Department Club Ltd | Hospitality | 2021 |
| THE Draytons Freeholders (London) Ltd | Financial services | 2026 |
| THE Enterprise Centre (ST Albans) Limited | Administrative & support | 2015 |
| THE European Pension Fund Investment Forum Limited | Other services | 1995 |
| THE First Artist Company Limited | Arts & recreation | 2005 |
| THE G & L Property Partnership LLP | | 2004 |
| THE Golf Club House Limited | Wholesale & retail | 2024 |
| THE Guard Family LLP | | 2013 |
| THE Gym & Tonic Club Limited | Arts & recreation | 2017 |
| THE Hair Barn Radlett Ltd | Other services | 2024 |
| THE High END Chauffeurs Ltd | Transport & logistics | 2026 |
| THE House of Kandinof Ltd | Financial services | 2024 |
| THE Hub Office Space Limited | Real estate | 2018 |
| THE Kinc Management Limited | Arts & recreation | 2014 |
| THE LEE Smith Foundation Limited | Health & social care | 2006 |
| THE Lodge (Harefield) Management Company Ltd | Households | 2003 |
| THE London Centre for Advanced Pain Management Limited | Professional & scientific | 2007 |
| THE Nail Base Limited | Wholesale & retail | 2002 |
| THE Old London Moving Company Limited | Transport & logistics | 1992 |
| THE Oval Partnership Architecture Ltd | Professional & scientific | 2010 |
| THE Pension Fund Investment Forum Limited | Other services | 2004 |
| THE Radlett Deli Limited | Wholesale & retail | 2012 |
| THE Raspberry Picture Company Limited | Information & communication | 2003 |
| THE Service Station Limited | Professional & scientific | 2009 |
| THE Standen Organisation Ltd | Professional & scientific | 2009 |
| THE Vegetarian Chef Ltd | Manufacturing | 2021 |
| THE Warren (Radlett) Limited | Households | 2018 |
| THE Watford Property Company Limited | Real estate | 1998 |
| THE Wellbeing Cognoscente Limited | Other services | 2021 |
| Thebrownhouse Limited | Real estate | 2015 |
| Thelusson Court Limited | Households | 1974 |
| Thermasash Ltd | Construction | 2018 |
| Three Rivers Solutions Limited | Information & communication | 2022 |
| Threesixtyone Ltd | Real estate | 2017 |
| Tiger Properties Limited | Real estate | 1953 |
| Timeless Collectibles Limited | Wholesale & retail | 2024 |
| Timray Limited | Real estate | 1990 |
| TIN MAN Group Limited | Financial services | 2020 |
| TIN Sky Investments Limited | Financial services | 2020 |
| Tiny PIE Ltd | Wholesale & retail | 2016 |
| Titan Consulting Ltd | Professional & scientific | 2023 |
| Tivorytrading Ltd | Wholesale & retail | 2023 |
| TJM Reporting Limited | Professional & scientific | 2017 |
| TKR Capital Limited | Real estate | 2020 |
| Tony's Removals Limited | Administrative & support | 1994 |
| Topluck Limited | Health & social care | 2020 |
| Toto London Limited | Wholesale & retail | 2020 |
| Toureen Divine Mercy | Administrative & support | 2016 |
| Toureen ICP Power Ltd | Construction | 2013 |
| Toureen Properties Limited | Construction | 2009 |
| Toureen Retail Limited | Construction | 1994 |
| Tova Properties Limited | Real estate | 2017 |
| TPL Holdings Limited | Financial services | 2019 |
| TR Design Group Ltd | Wholesale & retail | 2021 |
| Track'D Ltd. | Information & communication | 2023 |
| Tracyb Ltd | Professional & scientific | 2022 |
| Transact Client Group Ltd | Wholesale & retail | 2025 |
| Transmedia Pictures Ltd | Administrative & support | 2025 |
| Transnational Investments Limited | Professional & scientific | 2023 |
| Travel JAB Ltd | Information & communication | 2016 |
| Treebond Limited | Real estate | 2003 |
| Trichology Interactive Limited | Education | 2024 |
| Trigletts Ltd | Real estate | 2024 |
| Trinity Lighting UK Ltd | Extraterritorial | 2012 |
| Tristev Finance Limited | Information & communication | 2007 |
| TRL Holdings Limited | Administrative & support | 2019 |
| Trustech Group (UK) Limited | Information & communication | 2024 |
| TT Advisory Limited | Professional & scientific | 2026 |
| Tudor Road Estate (London) Limited | Real estate | 1957 |
| Tudorwhite Ltd | Information & communication | 2002 |