| Tissue for Research Ltd | Professional & scientific | 2014 |
| Titan Foods Limited | Hospitality | 2002 |
| TLA Properties and Investments Ltd | Real estate | 2025 |
| Tlhb Ltd | Administrative & support | 2025 |
| Tmjb Investments Limited | Construction | 2023 |
| TML Consulting Limited | Real estate | 2015 |
| TML Properties (Newmarket) Limited | Extraterritorial | 2023 |
| TN Ltd | Extraterritorial | 2024 |
| Tnts Empires Ltd | Administrative & support | 2025 |
| TO Ltd | Extraterritorial | 2009 |
| Tobacco Box Limited | Wholesale & retail | 2010 |
| Tofino Investments Limited | Real estate | 2016 |
| TOG (Ickleford) Limited | Hospitality | 1989 |
| Tomas&Rasma Ltd | Transport & logistics | 2019 |
| Tommybuild Ltd | Construction | 2022 |
| Tomu Digital Marketing & Software Development and Consulting Ltd | Information & communication | 2019 |
| Top Dog Powerhouse Ltd | Arts & recreation | 2025 |
| Top Line Fertiliser Limited | Extraterritorial | 1994 |
| Top Notch Cars Limited | Transport & logistics | 2019 |
| Topschool.Ai UK Ltd | Information & communication | 2026 |
| Total Decorating Solutions Ltd | Construction | 2010 |
| Total Lift Scaffolding Limited | Construction | 2021 |
| Touchtile Limited | Professional & scientific | 2005 |
| Tpkm Property Ltd | Real estate | 2023 |
| Tracca-Uk Limited | Professional & scientific | 2016 |
| Tradegreat Limited | Professional & scientific | 1983 |
| Trafalgar Farming Limited | Agriculture & fishing | 2016 |
| Transact Limited | Other services | 2020 |
| Treble 9 Limited | Professional & scientific | 2024 |
| Trees Treatment Rooms Limited | Other services | 2013 |
| Trenchgate Ltd | Administrative & support | 2024 |
| Trevor and Lynette Services Ltd | Health & social care | 2022 |
| Trillium Place Ltd | Real estate | 2003 |
| Triple 9 Group Limited | Manufacturing | 2013 |
| Triple Espresso Limited | Administrative & support | 2016 |
| Triple Star Fire Limited | Professional & scientific | 2010 |
| Trishul Limited | Real estate | 2009 |
| Tristel International Limited | Manufacturing | 2011 |
| Tristel PLC | Professional & scientific | 2003 |
| Tristel Solutions Limited | Manufacturing | 1998 |
| Trivoh Limited | Information & communication | 2024 |
| TRP Events Ltd | Hospitality | 2024 |
| Trubuild Cambridgeshire Limited | Construction | 2026 |
| Trucktekk Limited | Wholesale & retail | 2021 |
| Truefix Construction Limited | Administrative & support | 2022 |
| Trulybu Ltd | Education | 2022 |
| TS Essex Limited | Wholesale & retail | 2022 |
| TTR Bloodstock Limited | Arts & recreation | 2022 |
| Tudorprime Limited | Extraterritorial | 1988 |
| Tuesday Ltd | Extraterritorial | 2010 |
| Tupu Ltd. | Professional & scientific | 2018 |
| Turf Terrace Ltd | Financial services | 2025 |
| Turing Experts Limited | Financial services | 2014 |
| Turkoman New Ltd | Hospitality | 2024 |
| Turkoman Racing Ltd | Transport & logistics | 2025 |
| Turners (Soham) Holdings Limited | Transport & logistics | 2011 |
| Turners (Soham) Service Company Limited | Administrative & support | 1996 |
| Turners Britannia Parks Limited | Administrative & support | 2009 |
| Turners Cotswold Manor Country Park LLP | | 2008 |
| Turners Landex Parks Limited | Real estate | 2010 |
| Turners Orchard Park Limited | Professional & scientific | 2024 |
| Turners Parks Group Limited | Professional & scientific | 2011 |
| Turners Regency Parks Limited | Real estate | 2009 |
| TV Ltd | Extraterritorial | 2009 |
| TW Developements Limited | Real estate | 2023 |
| TW Limited | Extraterritorial | 2008 |
| TW Media & Creative Limited | Information & communication | 2022 |
| TWC-N2 Limited | Hospitality | 2022 |
| Tweeting Nest Properties Limited | Real estate | 2024 |
| Twelve Noon Films Limited | Information & communication | 2022 |
| Twelve Point Limited | Manufacturing | 2003 |
| Twenty Two Construction Limited | Construction | 2021 |
| Twentypence Limited | Administrative & support | 2013 |
| Twentypence Property Limited | Real estate | 2024 |
| Twin Dots Labs Limited | Information & communication | 2025 |
| Twiza for the People in Need Ltd | Health & social care | 2014 |
| TWP Invest Ltd | Real estate | 2019 |
| TY Ltd | Extraterritorial | 2009 |
| UBG Investments Limited | Financial services | 2023 |
| UC Ltd | Extraterritorial | 2020 |
| Ufac (U.K.) Limited | Manufacturing | 1976 |
| Ufac Holdings Limited | Manufacturing | 2016 |
| Ugasgroup Ltd | Transport & logistics | 2026 |
| UHF Equine Ltd | Professional & scientific | 2024 |
| UK Card Shows Ltd | Wholesale & retail | 2025 |
| UK Trading Card Games Ltd | Wholesale & retail | 2022 |
| Uk-China Culture & Technology Exchange Limited | Information & communication | 2013 |
| Uk-China Culture and Technology Exchange Association | Information & communication | 2010 |
| Ukaliq Ltd | Real estate | 2016 |
| Ultima Trading Limited | Wholesale & retail | 2024 |
| Ultramacro Ltd | Manufacturing | 2018 |
| UMA Sushi Ltd | Hospitality | 2026 |
| Unanimity Limited | Professional & scientific | 2019 |
| Unex (NO. 1) Limited | Real estate | 2009 |
| Unex (NO. 10) Limited | Real estate | 2015 |
| Unex (NO. 13) Limited | Construction | 2020 |
| Unex (NO. 14) Limited | Construction | 2020 |
| Unex (NO. 15) Limited | Construction | 2020 |
| Unex (NO. 16) Limited | Construction | 2020 |
| Unex (NO. 17) Limited | Construction | 2020 |