| Topa FIX Ltd. | Construction | 2023 |
| Topgear Motorsports Ltd | Administrative & support | 2013 |
| Toppan Security Group Limited | Financial services | 2024 |
| Toppan Security Limited | Information & communication | 2019 |
| Toprak Grill Ltd | Hospitality | 2025 |
| Torino Overton Ltd | Hospitality | 2024 |
| Torma Decorating Limited | Construction | 2014 |
| Toseven Ltd | Information & communication | 2025 |
| Total Automotive Limited | Wholesale & retail | 2021 |
| Total Flooring (Basingstoke) Ltd | Construction | 2006 |
| Total Sense Limited | Real estate | 1999 |
| Toucan 5 Limited | Administrative & support | 2018 |
| Touchdown PR Limited | Professional & scientific | 2006 |
| Tovey Tax Ltd | Professional & scientific | 2025 |
| Town and Commercial Properties Limited | Construction | 2010 |
| Town Centre Mortgages (Basingstoke) Limited | Financial services | 2003 |
| Towtech Ltd | Wholesale & retail | 2019 |
| Toybee Ltd | Administrative & support | 2016 |
| TP Lifted Limited | Professional & scientific | 2018 |
| TPT Fire Maintenance Limited | Construction | 1990 |
| TPT Fire Projects Ltd. | Construction | 2004 |
| TPT Fire Solutions Ltd | Construction | 2024 |
| TPT Fire Systems Group Ltd. | Construction | 2004 |
| TQI Services Ltd | Construction | 2020 |
| Trace Blue RD Limited | Information & communication | 2018 |
| Traction Capital Finance Limited | Financial services | 2023 |
| Trade Genic Limited | Wholesale & retail | 2020 |
| Trade Worldwide Limited | Wholesale & retail | 2020 |
| Traducrea Limited | Professional & scientific | 2021 |
| Trainwithreece Limited | Arts & recreation | 2026 |
| Tranckle PMU Training Ltd | Education | 2022 |
| Trane Services Limited | Extraterritorial | 2003 |
| Trane UK Limited | Administrative & support | 1996 |
| Transact Yashvir Ltd | Wholesale & retail | 2025 |
| Transbank Card Services Limited | Extraterritorial | 2007 |
| Transform Smiles Limited | Health & social care | 2017 |
| TRANSFORMATION21ST Limited | Professional & scientific | 2015 |
| Transitivity Consultancy Limited | Professional & scientific | 2013 |
| Transmotors Limited | Wholesale & retail | 2014 |
| Transpower Applications Limited | Manufacturing | 1996 |
| Transpower Limited | Extraterritorial | 2007 |
| Transsend Payments Limited | Financial services | 2007 |
| Transworld Commodity Traders Limited | Wholesale & retail | 2024 |
| Trataka Events Ltd | Arts & recreation | 2025 |
| Travel Amigo Limited | Administrative & support | 2023 |
| Travel Angels Limited | Administrative & support | 2023 |
| Travelezzi Limited | Wholesale & retail | 2019 |
| Travelytes Ltd | Wholesale & retail | 2025 |
| Trelune UK Ltd | Wholesale & retail | 2025 |
| Trembeth Wealth Management LLP | | 2017 |
| TRH Improvements Ltd | Administrative & support | 2026 |
| Tridonic UK Limited | Manufacturing | 1966 |
| Triforce Security Solutions Limited | Administrative & support | 2009 |
| Trigomead Limited | Wholesale & retail | 1981 |
| Trihtbutum Limited | Professional & scientific | 2024 |
| Trinity Accountancy Services Ltd | Professional & scientific | 2014 |
| Trio Management Basingstoke Limited | Wholesale & retail | 2013 |
| Trio Management Estate Limited | Real estate | 2020 |
| Trio Management Limited | Wholesale & retail | 2012 |
| Trio Management Norn Hill Limited | Wholesale & retail | 2016 |
| Triple Portion Limited | Other services | 2018 |
| Triple R Consultants Limited | Professional & scientific | 2013 |
| Triple R Properties Ltd | Real estate | 2019 |
| Triton Link Ltd | Transport & logistics | 2019 |
| Tritrade Limited | Real estate | 2013 |
| Triumph Partnerships (UK) LP | | 2004 |
| Troubleshooting Ltd | Professional & scientific | 2023 |
| Trsko Limited | Wholesale & retail | 2022 |
| TRU Insurance Services Limited | Financial services | 2022 |
| Truck Trailer Ltd | Transport & logistics | 2024 |
| Trudell Medical UK Limited | Financial services | 2016 |
| True Albion Ltd | Wholesale & retail | 2026 |
| True Care Personnel Ltd. | Health & social care | 2017 |
| True Tathata Ltd | Other services | 2026 |
| Trust a Carer Limited | Health & social care | 2016 |
| Trust IT Solutions (2012) Limited | Information & communication | 2012 |
| Trusthaus Limited | Information & communication | 2026 |
| Trustlayer Limited | Information & communication | 2014 |
| Trustmark (2005) Limited | Other services | 2005 |
| Trusty Care Limited | Health & social care | 2026 |
| Trusty Cleaning Solutions Ltd | Transport & logistics | 2016 |
| Trusty Parts Ltd | Energy | 2018 |
| TS Design Solutions Ltd | Information & communication | 2025 |
| Tsavage Limited | Information & communication | 2015 |
| Tsci UK Limited | Real estate | 2020 |
| TSL Lighting Limited | Professional & scientific | 2007 |
| TSP Brokerage Limited | Financial services | 2024 |
| TT Events Ltd | Other services | 2018 |
| TT IT Limited | Information & communication | 2008 |
| Ttbasingstoke Ltd | Manufacturing | 2021 |
| TTS Partners Ltd | Wholesale & retail | 2020 |
| TTS Services Ltd | Professional & scientific | 2025 |
| Tubbs Cosmetics Ltd | Wholesale & retail | 2014 |
| Tulba Consulting Limited | Professional & scientific | 2017 |
| Tulip Recruitment Group Limited | Administrative & support | 1999 |
| Turbine Developments (Kennel Farm) Limited | Real estate | 2021 |
| Turbine Developments (Reading Road) Limited | Real estate | 2025 |
| Turbine Developments Limited | Financial services | 2020 |
| Turbo Controls Limited | Extraterritorial | 2020 |
| Turtle Beach Europe Limited | Wholesale & retail | 1999 |