| Top Flight Flooring Limited | Construction | 2021 |
| Top MAN DRY Cleaner & Ironing Service Limited | Other services | 2022 |
| Top Tiler London Ltd | Construction | 2013 |
| Top-Notch Sprayer Ltd | Construction | 2017 |
| Topcut Barber (Dunstable) Limited | Other services | 2022 |
| Topcut Dunstable Ltd | Other services | 2026 |
| Toplead Consulting Ltd | Information & communication | 2011 |
| Toplead Properties Ltd | Real estate | 2019 |
| Toplight Limited | Manufacturing | 1988 |
| Topmod Limited | Administrative & support | 2025 |
| Torque Communications & Training Ltd | Education | 2013 |
| TORQUE2 Limited | Professional & scientific | 2011 |
| TORQUE4 Limited | Information & communication | 2018 |
| Tota Limited | Information & communication | 2016 |
| Tota Property Management Ltd | Real estate | 2023 |
| Total Data Solutions Ltd | Information & communication | 2019 |
| Total Packaging Solutions Worldwide Ltd | Administrative & support | 2022 |
| Total Systems Management Limited | Information & communication | 1998 |
| Totalshield Solutions Limited | Construction | 2024 |
| Totalsite Management Ltd | Construction | 2026 |
| Totternhoe Stone Restoration Ltd | Manufacturing | 2022 |
| Toucan Lettings Ltd | Real estate | 2024 |
| Tour Best Design Limited | Professional & scientific | 2008 |
| Town Bites Limited | Hospitality | 2024 |
| Townsend Consultancy and Design Limited | Professional & scientific | 2014 |
| Toyboy Warehouse Limited | Other services | 2007 |
| TPH Homes Limited | Real estate | 2020 |
| TPZ Limited | Wholesale & retail | 2025 |
| TR Property Solutions Ltd | Real estate | 2018 |
| Tr&L Ltd | Administrative & support | 2013 |
| TRACER7 Ltd | Information & communication | 2011 |
| Trade & Build Limited | Extraterritorial | 2024 |
| Trade Cars Essex Limited | Wholesale & retail | 2019 |
| Trade Frame Hub Limited | Wholesale & retail | 2025 |
| Trade Promotion Limited | Professional & scientific | 2025 |
| Tradecrafts & Digital Solutions Ltd | Construction | 2014 |
| Tradewinds 23.5 Limited | Professional & scientific | 2010 |
| Traditional Component Scaffolding Ltd | Construction | 2010 |
| Traditional Taste Limited | Hospitality | 2025 |
| Tranico Limited | Arts & recreation | 2021 |
| Tranquil Escapes MMT Ltd | Other services | 2024 |
| Trans Haul (Europe) Limited | Transport & logistics | 2005 |
| Trans Yellow Arrow Ltd | Transport & logistics | 2016 |
| Trans-Kriss Ltd | Administrative & support | 2017 |
| Transfermybills.Com Ltd | Information & communication | 2017 |
| Transgeo Ltd | Transport & logistics | 2013 |
| Transport Services M B Ltd | Transport & logistics | 2025 |
| Transporting Trade Limited | Transport & logistics | 2025 |
| Transportvibe Ltd | Transport & logistics | 2024 |
| Transunu Ltd | Transport & logistics | 2015 |
| Transwift Ltd | Transport & logistics | 2015 |
| Transylvania GG Ltd | Wholesale & retail | 2021 |
| Travel 365 DMC Ltd | Administrative & support | 2023 |
| Travel Project Events Ltd | Hospitality | 2024 |
| Travel With Sharon Limited | Administrative & support | 2023 |
| Treasures Business Empire Limited | Other services | 2021 |
| Trevend Ltd | Wholesale & retail | 2025 |
| Tria Development Ltd | Construction | 2024 |
| Tricrescent Property Limited | Administrative & support | 2021 |
| Trilogy Food Service Limited | Wholesale & retail | 2023 |
| Trio Cleaning Ltd | Construction | 2015 |
| Trio Hairdressing Salon Ltd | Other services | 2020 |
| Triple a Estate Limited | Real estate | 2022 |
| TRIPLE3 Ealing Ltd | Hospitality | 2024 |
| Tripp Aviation Limited | Manufacturing | 2022 |
| Trofim Logistics Limited | Transport & logistics | 2023 |
| Tropical Holdings Limited | Real estate | 2019 |
| Tropical Rain Limited | Real estate | 2019 |
| TRU Thrive Limited | Education | 2025 |
| True Inspiration Limited | Education | 2022 |
| Trueglam UK Ltd | Wholesale & retail | 2021 |
| Truesite Properties Ltd | Real estate | 2025 |
| Trufflemen Ltd | Agriculture & fishing | 2022 |
| Trustec Consultancy Ltd | Real estate | 2020 |
| Trustedtrans Ltd | Transport & logistics | 2020 |
| TS Impact Limited | Construction | 2025 |
| TSA Car Sales Ltd | Wholesale & retail | 2018 |
| TT Logis Ltd | Transport & logistics | 2019 |
| TU Motors Limited | Wholesale & retail | 2018 |
| Tudor DB Ltd | Construction | 2020 |
| Tulay Chef Limited | Hospitality | 2022 |
| Tuneng Ltd | Professional & scientific | 2024 |
| Turgelstar Enterprises Limited | Real estate | 1982 |
| Turkish Barber Dunstable Ltd | Other services | 2023 |
| Turkish Traditional BBQ Limited | Hospitality | 2022 |
| Turn Partners Limited | Professional & scientific | 2013 |
| Tutors Gate (Aylesbury) Management Company Limited | Households | 2012 |
| Tutti Toot Ltd | Professional & scientific | 2020 |
| Twarniespecials Soup Kitchen CIC | Hospitality | 2026 |
| Twigga Limited | Wholesale & retail | 2025 |
| Twilight Shift Limited | Information & communication | 2023 |
| Twmsp Ltd | Hospitality | 2023 |
| Two Courts Limited | Real estate | 1986 |
| TWP Flooring Limited | Wholesale & retail | 2014 |
| Tynad and Hills Limited | Administrative & support | 2016 |
| Tyra Builders Limited | Construction | 2017 |
| U&U Skips Ltd | Water & waste | 2020 |
| U.K. Implant Manufacturing Co. Limited | Health & social care | 2002 |
| Uberplumb Ltd | Construction | 2019 |
| UC Expert Ltd | Information & communication | 2012 |