| TRANS4NATIONUK CIC | Other services | 2017 |
| Transax Networks Ltd | Wholesale & retail | 2019 |
| Transbank Services Ltd | Professional & scientific | 2003 |
| Transcentury Ltd | Transport & logistics | 2019 |
| Transforclean Services Limited | Administrative & support | 2026 |
| Transforwise Limited | Information & communication | 2025 |
| Transporter FQ Ltd | Transport & logistics | 2024 |
| Transportor Ltd | Wholesale & retail | 2023 |
| Travel HUT ( Cranbrook) Ltd | Administrative & support | 2022 |
| Travel in My Space Ltd | Transport & logistics | 2025 |
| Traxon Services Limited | Extraterritorial | 2002 |
| Treacher Properties Limited | Households | 2009 |
| Treading Energy Centre Limited | Energy | 2022 |
| Treasure Finance Limited | Real estate | 2005 |
| Treegram Limited | Extraterritorial | 1989 |
| Treesave Reclamation Ltd | Construction | 2001 |
| Tregaron Investments Limited | Construction | 1963 |
| Trendiah Ltd | Wholesale & retail | 2025 |
| Trendzzo Ltd | Wholesale & retail | 2024 |
| Trentvalley Limited | Information & communication | 1995 |
| Trenzio Ltd | Wholesale & retail | 2026 |
| Tribrid Packaging Ltd | Administrative & support | 2025 |
| Trident Tyre & Vehicle Services Limited | Administrative & support | 2007 |
| Triland Limited | Administrative & support | 2006 |
| Trinexa Innovations Ltd | Manufacturing | 2017 |
| Triniti Homes Limited | Professional & scientific | 2005 |
| Trionex Commerce Ltd | Wholesale & retail | 2026 |
| Triple a Pathway Limited | Hospitality | 2025 |
| Triple EL Ltd | Real estate | 2024 |
| Triple R Railway Engineering Limited | Transport & logistics | 2007 |
| TRIPLE6 Films Ltd | Information & communication | 2025 |
| Triplegate Global Sources Limited | Wholesale & retail | 2003 |
| Triplestar Apartment Ltd | Real estate | 2025 |
| Triton Electronics Limited | Manufacturing | 1963 |
| Triumvirate Technology Limited | Information & communication | 1993 |
| TRN (Train) Holdings Limited | Financial services | 2018 |
| Trochetia Care Services Ltd | Health & social care | 2023 |
| Trojan Tools (UK) Limited | Wholesale & retail | 1996 |
| Trojan Woodcraft Limited | Construction | 2005 |
| Trombe Limited | Professional & scientific | 2005 |
| Tropical Partners Ltd | Manufacturing | 2018 |
| TRU Count, Inc UK Limited | Wholesale & retail | 2024 |
| Truck-Lite Europe Limited | Manufacturing | 1924 |
| Truckcare (Purfleet) Limited | Wholesale & retail | 2000 |
| Trulex Limited | Professional & scientific | 2004 |
| Truwork Limited | Administrative & support | 2022 |
| TS Entrepreneurship and Trade Ltd | Wholesale & retail | 2023 |
| Tshirt AZ Ltd | Wholesale & retail | 2021 |
| TTR Roofing Ltd | Construction | 2023 |
| TTS Takeaway Limited | Wholesale & retail | 2024 |
| TTT Foods Ltd | Hospitality | 2026 |
| Tubbenden Computer Services Limited | Professional & scientific | 1979 |
| Tubocare Limited | Health & social care | 2025 |
| Tucker Bros. Limited | Wholesale & retail | 1956 |
| Tudor Owen Photography Limited | Arts & recreation | 1999 |
| Tuga Holding London Ltd | Financial services | 2024 |
| Tuition Hub Ltd | Education | 2024 |
| Tule Ltd | Wholesale & retail | 2024 |
| Tulkinghorn Trading Limited | | 1953 |
| Tuneware Limited | Households | 1985 |
| Tusk Transport GB Limited | Transport & logistics | 2018 |
| TVL Engineering Ltd | Professional & scientific | 2021 |
| TVM Accountancy Ltd | Professional & scientific | 2018 |
| Twelvebillion Limited | Professional & scientific | 2016 |
| Two Aces Properties Limited | Real estate | 2002 |
| Two Brewers Catering Limited | Hospitality | 2025 |
| Two Carrick Ltd | Financial services | 2026 |
| Two Sheds Limited | Professional & scientific | 2005 |
| TY Services Ltd | Wholesale & retail | 2020 |
| Tycraft Limited | Health & social care | 2002 |
| Tydeman & Sons Limited | Construction | 1947 |
| TYN39 Ltd | Wholesale & retail | 2020 |
| Tyndale Properties Limited | Hospitality | 2007 |
| Tyrell Carpentry Contractors Limited | Construction | 2007 |
| TZA Services Ltd | Construction | 2024 |
| U & I Ijeneme Consults Ltd | Health & social care | 2009 |
| U DOT Ltd | Administrative & support | 2025 |
| U GEN Limited | Professional & scientific | 2010 |
| U Store Solutions Limited | Transport & logistics | 2003 |
| UAA Limited | Wholesale & retail | 2021 |
| Ubermagictwo Limited | Information & communication | 2007 |
| Ubran Apex London Ltd | Wholesale & retail | 2025 |
| Uc-Homes Developments Ltd | Real estate | 2025 |
| UCHANGE4BETTER Limited | Information & communication | 2004 |
| Uchejides Limited | Health & social care | 2025 |
| UCO Medicals Ltd | Public administration | 2025 |
| UK Airport Taxi Ltd | Administrative & support | 2025 |
| UK Asia Trade Ltd | Wholesale & retail | 2015 |
| UK Blending Limited | Manufacturing | 1999 |
| UK Colossal Limited | Other services | 2005 |
| UK Commerce Solution Ltd | Wholesale & retail | 2025 |
| UK Doorware Ltd | Manufacturing | 2019 |
| UK Eggs Ltd | Wholesale & retail | 2007 |
| UK Glassforce Ltd | Construction | 2006 |
| UK Hair Styles Limited | Other services | 2018 |
| UK Happpy Cart Ltd | Wholesale & retail | 2025 |
| UK Medical Industries Ltd | Administrative & support | 2013 |
| UK Private Real Estate Ltd | Real estate | 2025 |
| UK Resilient Pathways CIC | Education | 2026 |
| UK Skyline Limited | Wholesale & retail | 2020 |