| Treehouse Life Ltd | Construction | 2015 |
| Tregair Limited | Administrative & support | 2003 |
| Trend Moda Ltd | Wholesale & retail | 2014 |
| TREND360 Ltd | Wholesale & retail | 2024 |
| Trendspire Global Ltd | Wholesale & retail | 2026 |
| Tresta Property Finance Limited | Financial services | 2025 |
| TRG Law Limited | Public administration | 2012 |
| TRH Design Ltd | Professional & scientific | 2020 |
| Tribe Inc. Ltd | Administrative & support | 2003 |
| Tribe Talent Ltd | Arts & recreation | 2020 |
| Tricia's Wigs Limited | Wholesale & retail | 2017 |
| Trics Consortium Limited | Information & communication | 2014 |
| Trifolium Ltd | Professional & scientific | 2015 |
| Trikha Consulting Limited | Financial services | 2016 |
| Trikha Property Management Limited | Real estate | 2023 |
| Trimount Properties (Brooklyn) Limited | Construction | 2016 |
| Trimount Properties Limited | Administrative & support | 1992 |
| Trimount Residential Limited | Real estate | 2000 |
| Trinacria Contractors Ltd | Construction | 2015 |
| Tringham Cottages (West END) Management Company Limited | Households | 1989 |
| Trinicto Limited | Manufacturing | 2023 |
| Trinity of London Limited | Manufacturing | 2004 |
| Trinity Physiotherapy Ltd | Health & social care | 2020 |
| Trio’S Care Ltd | Public administration | 2023 |
| Tripsmiths Travel Limited | Administrative & support | 2026 |
| Triskelion Counselling & Psychotherapy Ltd | Health & social care | 2023 |
| Trojan Consultants Limited | Information & communication | 1981 |
| Tronbot Prop Limited | Real estate | 2021 |
| Trot Together Ltd | Agriculture & fishing | 2025 |
| Trouthouse Developments Ltd | Real estate | 2023 |
| Trowan Farm Management Company Limited | Hospitality | 2008 |
| Troy Phoenix Ltd | Construction | 2026 |
| Trubuild Building Services Limited | Construction | 2017 |
| True Properties Ltd | Real estate | 2019 |
| Truepath Advisory Ltd | Information & communication | 2026 |
| Truerights Ltd | Professional & scientific | 2024 |
| Trugile Ai-First Technologies Ltd | Information & communication | 2026 |
| Trumps Drycleaners Limited | Other services | 2014 |
| Trustconnect Ltd | Information & communication | 2024 |
| Tsam Associates Ltd | Professional & scientific | 2012 |
| Tshh Consulting Limited | Administrative & support | 2015 |
| TSK at Caramel Ltd | Manufacturing | 2019 |
| TSP Construction Ltd | Construction | 2014 |
| TT Property Solutions Ltd | Construction | 2013 |
| TTA Management Limited | Financial services | 1994 |
| TTA Travel | Other services | 1993 |
| TTA Trustees (UK) Limited | Professional & scientific | 2001 |
| TTA Worldchoice Limited | Professional & scientific | 2008 |
| Ttafs Ltd | Financial services | 2010 |
| Ttng Investments Limited | Financial services | 2015 |
| Ttng Transport Limited | Transport & logistics | 2016 |
| Tuan Limited | Administrative & support | 1974 |
| Tudorabbey (UK) Limited | Construction | 1996 |
| Tuga Store Ltd | Hospitality | 2018 |
| Tulk Residents Management Company Limited | Administrative & support | 1983 |
| Tunsgate Cars Ltd | Transport & logistics | 2024 |
| Turf Advisory Solutions Limited | Arts & recreation | 2021 |
| Turf Machinery (Contracts) Limited | Arts & recreation | 1996 |
| Turf Machinery (Spares) Limited | Wholesale & retail | 1996 |
| Turf Machinery Engineering LLP | | 2010 |
| Turfscapes Ltd | Administrative & support | 2020 |
| Turiya Limited | Information & communication | 2025 |
| Turkish Barber Horsell Ltd | Other services | 2024 |
| Turning the Page Ltd | Professional & scientific | 2021 |
| Turnoak Interim Management Limited | Administrative & support | 1999 |
| Turquoise Cars Ltd | Transport & logistics | 2025 |
| Tvanna's Catering Company Limited | Hospitality | 2022 |
| Tvizi Ltd | Administrative & support | 2024 |
| TVT Group Ltd | Financial services | 2018 |
| TW Building Ltd | Construction | 2025 |
| TW Dogs Ltd | Other services | 2022 |
| Twelve Assured Ltd | Wholesale & retail | 2022 |
| Twin Mechanics Ltd | Wholesale & retail | 2025 |
| Twisted Stem Ltd | Agriculture & fishing | 2025 |
| Twitchen Estates Limited | Households | 1994 |
| Two and Two Trading Limited | Other services | 2014 |
| Two Feet Consulting Ltd | Professional & scientific | 2025 |
| Two Fifty Four Training Limited | Professional & scientific | 2021 |
| Two TEN Ltd | Hospitality | 2024 |
| Two Wolves Limited | Professional & scientific | 2015 |
| Twolf Ltd | Manufacturing | 2022 |
| TWS Innovations Limited | Manufacturing | 2013 |
| TWS Manufacturing Limited | Manufacturing | 2016 |
| Tycec Ltd | Professional & scientific | 2022 |
| Tykhie Consulting Limited | Wholesale & retail | 2014 |
| Tyson Associates Ltd | Administrative & support | 2014 |
| Tyson Carpentry & Joinery Limited | Construction | 2013 |
| Uaca Limited | Education | 2025 |
| Uber Games Limited | Wholesale & retail | 2020 |
| Ubisoft Limited | Information & communication | 1989 |
| UDN Logistics Limited | Transport & logistics | 2025 |
| UDS Associates Ltd | Professional & scientific | 2018 |
| Ufbs Group Ltd | Financial services | 2021 |
| UFBS1 Limited | Other services | 2022 |
| UFBS2 Ltd | Other services | 2021 |
| UFBS3 Limited | Health & social care | 2025 |
| Ufcon Limited | Other services | 2024 |
| UK Activkids Limited | Education | 2026 |
| UK Brands Shop Ltd | Wholesale & retail | 2024 |
| UK Commercial & Domestic Appliances Ltd | Manufacturing | 2017 |