| Torkore Portfolio Limited | Financial services | 2020 |
| Toroadvisorpro Ltd | Education | 2025 |
| Total Design Group Ltd | Financial services | 2017 |
| Total Design Holdings Limited | Financial services | 2021 |
| Total Design Joinery Ltd | Construction | 2016 |
| Total Design Passive Fire Solutions Ltd | Construction | 2023 |
| Total Design Shopfitting Services Limited | Construction | 1999 |
| Total Process Fluids Limited | Wholesale & retail | 2009 |
| Totton Motor Company Ltd | Wholesale & retail | 2024 |
| Tourism Management Institute | Professional & scientific | 2016 |
| Tourmaline Properties Limited | Real estate | 2025 |
| Town and Country LET Ltd | Real estate | 2011 |
| TPS505 Ltd | Information & communication | 2025 |
| Tracey Dunning at Chuckles and Care Limited | Health & social care | 2015 |
| Trade Cleaning Machines and Hire Limited | Wholesale & retail | 2012 |
| Trade Point Limited | Extraterritorial | 2008 |
| Trade Together Ltd | Wholesale & retail | 2010 |
| Tradecore International Limited | Wholesale & retail | 2015 |
| Traka Ltd | Construction | 2020 |
| Trakart Properties & Design Limited | Construction | 2005 |
| Tramar Developments & Construction Ltd | Construction | 2006 |
| Tramar Homes Ltd | Extraterritorial | 2013 |
| Transairport Limited | Transport & logistics | 2008 |
| Transalis Limited | Information & communication | 2002 |
| Transcare Team Limited | Transport & logistics | 2012 |
| Transform Your Profits Ltd | Professional & scientific | 2019 |
| Transgrom Ltd | Transport & logistics | 2017 |
| Transmobility Ltd | Transport & logistics | 2008 |
| Transylvanian Ltd | Transport & logistics | 2018 |
| Trapezium Innovations Ltd | Professional & scientific | 2021 |
| Travelism Limited | Information & communication | 2001 |
| Trecol Limited | Professional & scientific | 2023 |
| Tree Menders People Limited | Agriculture & fishing | 2008 |
| TRI Locality Care (TLC) Limited | Health & social care | 2014 |
| Tri-Consultancy Limited | Education | 2023 |
| Trianna Medical Services Ltd | Health & social care | 2017 |
| Trilbys (Berkshire) Limited | Other services | 2014 |
| Trilbys (Hampshire) Limited | Other services | 2011 |
| Trinity IT Solutions Ltd | Information & communication | 2025 |
| Trinity Park (Garston Road) Management Limited | Households | 2010 |
| Trinity Rose Architecture Ltd | Professional & scientific | 2015 |
| Trinity Rose Limited | Professional & scientific | 2014 |
| Trintech Solutions Limited | Information & communication | 1992 |
| Tripkit Ltd | Information & communication | 2013 |
| Tripleguns Limited | Arts & recreation | 2025 |
| Tripod Mapping Surveys Limited | Administrative & support | 2018 |
| Trish Mullenberg Limited | Education | 2023 |
| Triton Safety Limited | Professional & scientific | 2018 |
| Triumph Property Limited | Real estate | 1985 |
| Trivora Innovation Ltd | Wholesale & retail | 2025 |
| TRL Plant Limited | Administrative & support | 2005 |
| Troop. Assemble. Ltd | Administrative & support | 2021 |
| Trowel Workz Limited | Construction | 2021 |
| TRU (UK) Noteholder Limited | Professional & scientific | 2013 |
| Truckgleam (UK) Limited | Other services | 2008 |
| True Innovation Estates Ltd | Real estate | 2026 |
| True Innovation Group Ltd | Professional & scientific | 2021 |
| Truespace Ltd | Construction | 2024 |
| Truffle PIG Holdings Ltd | Information & communication | 2019 |
| Truly HR Ltd | Administrative & support | 2024 |
| Trust Power Limited | Energy | 2016 |
| Trustline School Transport Ltd | Transport & logistics | 2026 |
| Truvion Healthcare Limited | Manufacturing | 2024 |
| TRY TRI Events Limited | Arts & recreation | 2012 |
| TSA Chambers Ltd | Professional & scientific | 2025 |
| TSL Technology Limited | Mining & quarrying | 1992 |
| TSN Holdings Limited | Construction | 2017 |
| TSN Homes Limited | Construction | 1996 |
| TSO Construction Limited | Construction | 2011 |
| TT Electronics IGT Limited | Manufacturing | 1987 |
| TU Haseen Limited | Hospitality | 2023 |
| Tudor Rose Property Management Ltd | Real estate | 2026 |
| Tullett Brown Limited | Professional & scientific | 2009 |
| Tunaz Properties Ltd | Real estate | 2025 |
| Turner Precision Testing Ltd | Professional & scientific | 2025 |
| Turner Squared Ltd | Professional & scientific | 2012 |
| Turnstone Associates LLP | | 2021 |
| Tvadswork Limited | Professional & scientific | 2023 |
| Twickenham Rugby Football Club (Trading) Limited | Arts & recreation | 2016 |
| Twickenham Rugby Football Club Limited | Arts & recreation | 2016 |
| Twinkle Care Limited | Health & social care | 2022 |
| Two Gills Limited | Hospitality | 2003 |
| Twohills Ltd | Construction | 2021 |
| Twyford G Ltd | Hospitality | 2026 |
| Twyford Waterworks Trust(The) | Education | 1985 |
| TYE Holdings Ltd | Real estate | 2020 |
| UDO Audio Ltd | Manufacturing | 2018 |
| UK Boxes Ltd | Wholesale & retail | 2020 |
| UK Ground Transportation Services Limited | Transport & logistics | 2024 |
| UK Plumb Heat Ltd | Construction | 2014 |
| UK Property Consulting Ltd | Extraterritorial | 2016 |
| UK Radio Portal Limited | Information & communication | 2022 |
| Ultimate Cleaning Ltd | Administrative & support | 2021 |
| UM Production Ltd | Professional & scientific | 2026 |
| Unatrics Ltd | Wholesale & retail | 2018 |
| Undersea Centre Limited | Manufacturing | 2018 |
| Underwood Barron Associates Limited | Professional & scientific | 1980 |
| Underwood Barron LLP | | 2008 |
| Underwood Eyecare Limited | Wholesale & retail | 2009 |
| Undisputed Fight League - UFL Limited | Arts & recreation | 2025 |