| Total Installations (Group) Limited | Construction | 2021 |
| Total Installations (Holdings) Limited | Financial services | 2021 |
| Totalfit UK Ltd | Education | 2024 |
| Totalpro Nurses Ltd | Administrative & support | 2020 |
| Totley Brook Limited | Professional & scientific | 2020 |
| Tots & Time OUT Limited | Health & social care | 2012 |
| TOUCAN52 Ltd | Administrative & support | 2026 |
| Touch of Paris Ltd | Wholesale & retail | 2017 |
| Towards Multimillionaire Limited | Construction | 2025 |
| Tower Launderette LLP | | 2021 |
| Town and Country Electrics Ltd | Construction | 2024 |
| Town and Country Services Ltd | Construction | 2022 |
| Town Mortgages Ltd | Financial services | 2024 |
| Town Property Holdings Limited | Financial services | 2018 |
| Town Property Limited | Real estate | 1998 |
| Townend Music Limited | Information & communication | 2000 |
| Towner | Education | 2013 |
| Towner Enterprises Limited | Wholesale & retail | 2013 |
| Towns Hotels Limited | Real estate | 1987 |
| TPC Health Ltd | Professional & scientific | 2016 |
| TPC Leadership Ltd | Professional & scientific | 2001 |
| Tpic Ltd | Real estate | 2025 |
| TQL Health Limited | Wholesale & retail | 2022 |
| TR Therapy Rooms Limited | Health & social care | 2019 |
| Tracy at the Travel Concept Ltd | Administrative & support | 2026 |
| Tradeonly.Net Limited | Information & communication | 2004 |
| Tradesmith Limited | Manufacturing | 1992 |
| Tradest Ltd | Wholesale & retail | 2022 |
| Tradipaints Limited | Wholesale & retail | 1994 |
| Traditional Medicinals Europe Ltd. | Extraterritorial | 2008 |
| Training, Playwork and Play CIC | Administrative & support | 2021 |
| Trak Property Management Services Limited | Real estate | 2018 |
| Tranquility Nails and Beauty Academy Ltd | Education | 2020 |
| Transactor Systems Ltd | Information & communication | 2001 |
| Transformancy Limited | Other services | 2018 |
| Translate & Communicate Limited | Professional & scientific | 2014 |
| Travel Dimensions Ltd | Administrative & support | 2021 |
| Travilearn Limited | Education | 2017 |
| Travolyo Ltd | Hospitality | 2026 |
| Trawlers Catering Limited | Hospitality | 2011 |
| Traynor ENT Ltd | Real estate | 2021 |
| Traynor Enterprises Ltd | Real estate | 2021 |
| Treasure Island (Eastbourne) Ltd | Professional & scientific | 2011 |
| Treecane Limited | Real estate | 2009 |
| Trendy Global Ltd | Other services | 2025 |
| Trendy Traders Ltd | Wholesale & retail | 2022 |
| Tres Amigos World Ltd | Hospitality | 2015 |
| TRI Thuc Holdings Ltd | Real estate | 2026 |
| Triangle Portfolio Limited | Real estate | 2005 |
| Tribune Group Limited | Manufacturing | 2014 |
| Trident Laundrettes Limited | Administrative & support | 2002 |
| Trident Nails & Beauty Limited | Other services | 2024 |
| Trident Properties UK Limited | Real estate | 2001 |
| Trident Restaurants Limited | Hospitality | 1998 |
| Trident Stores Ltd | Wholesale & retail | 2008 |
| Trimmer Education and Leadership Consultancy Ltd | Professional & scientific | 2026 |
| Trinitas.It Ltd | Hospitality | 2023 |
| Trinity Homes (UK) Holding Limited | Financial services | 2022 |
| Trinity House (Eastbourne) Limited | Households | 2007 |
| Trinity Street Limited | Hospitality | 1997 |
| Triple X Cleaning Ltd | Administrative & support | 2025 |
| Tripleplas Limited | Wholesale & retail | 2006 |
| Tripleplas Machinery Sales Limited | Wholesale & retail | 1970 |
| Triton Building Services (SE) Ltd | Construction | 2021 |
| Triton Fire and Security Ltd | Administrative & support | 2026 |
| Troika Projects Limited | Hospitality | 2023 |
| Trojan Assure Group Limited | Other services | 2025 |
| Trojan Designs Limited | Administrative & support | 2002 |
| Trowel Brickwork Ltd | Construction | 2025 |
| Troy's Tree and Hedge Services Limited | Administrative & support | 2025 |
| True Nails Limited | Other services | 2024 |
| True Training Ltd | Professional & scientific | 2019 |
| Truebyte International Limited | Other services | 2009 |
| Truebyte Limited | Information & communication | 2002 |
| Trueline Finishes Ltd | Construction | 2024 |
| Trueline Renovation Co Ltd | Construction | 2026 |
| Trujillo Court Ltd | Real estate | 2005 |
| Trujillo Court RTM Company Limited | Households | 2018 |
| Truscon Property Limited | Real estate | 2018 |
| Trust Security Solutions Limited | Administrative & support | 2022 |
| Trust Wills Limited | Other services | 2025 |
| Trustclub Limited | Administrative & support | 2002 |
| Trustexec (UK) Limited | Financial services | 2017 |
| Tsgk Ltd | Real estate | 2019 |
| Tsgk Plus Ltd | Construction | 2023 |
| TSL Homes Ltd | Real estate | 2025 |
| TSL Solutions Limited | Other services | 2025 |
| Tsmd Properties Ltd | Construction | 2019 |
| TSP 1 Limited | Financial services | 2020 |
| TSP 2 Limited | Professional & scientific | 2021 |
| TST (South East) Limited | Administrative & support | 2011 |
| TST Events Ltd | Hospitality | 2022 |
| TST Training Limited | Administrative & support | 2021 |
| TT Commercial Decorating Ltd | Construction | 2025 |
| TT Hurworth Limited | Health & social care | 2017 |
| TTA Southwark Taekwondo Limited | Arts & recreation | 2024 |
| TTA Taekwondo London Limited | Arts & recreation | 2020 |
| TTS Commercial Limited | Real estate | 2024 |
| Tubbs Computer Supplies CIC | Wholesale & retail | 2020 |
| Tucana Entertainments Limited | Arts & recreation | 2016 |