| Trading 26 Ltd | Real estate | 2025 |
| Tramfabriek Limited | Manufacturing | 2020 |
| Tran Property Services Ltd | Real estate | 2023 |
| Trans Eco Minerals and Mining Ltd | Mining & quarrying | 2012 |
| Transcen Limited | Professional & scientific | 2019 |
| Transform to Success Limited | Professional & scientific | 2011 |
| Transtour Travel Ltd | Administrative & support | 2022 |
| Travel Assets Group Limited | Professional & scientific | 2006 |
| Travelworks Ltd | Information & communication | 2026 |
| Treadgold Brock Limited | Professional & scientific | 2026 |
| Treasure Box Tales Ltd | Information & communication | 2024 |
| Treasury Link Limited | Financial services | 2020 |
| Trending Fashion Limited | Wholesale & retail | 2025 |
| Trevelyan Management Company Limited | Households | 2003 |
| Triad Properties Limited | Real estate | 1998 |
| Triaksha Consultants Ltd | Information & communication | 2018 |
| Triaksha Properties Limited | Real estate | 2024 |
| Tribe OUT Limited | Information & communication | 2017 |
| Trident & Co Properties Limited | Real estate | 2016 |
| Trident Partners Limited | Professional & scientific | 2011 |
| Trilliant Networks (UK) Ltd | Professional & scientific | 2009 |
| Trilliant Networks Operations (UK) Ltd. | Professional & scientific | 2018 |
| Trilouise Limited | Professional & scientific | 2007 |
| Trimidal Limited | Other services | 2016 |
| Trimurti Films International Limited | Information & communication | 1999 |
| Trinity Gate Freeholders Limited | Households | 2014 |
| Trinity Projects (Holdings) Limited | Professional & scientific | 2009 |
| Trinity Projects Limited | Administrative & support | 2009 |
| Triton Knight Ltd | Information & communication | 2011 |
| Trono Clothing Ltd | Wholesale & retail | 2019 |
| Troy (Energy Consultancy) Ltd | Professional & scientific | 2008 |
| Truck N BUS Technicians Ltd | Professional & scientific | 2014 |
| True Justice Limited | Professional & scientific | 2016 |
| True Wealth Ltd | Financial services | 2013 |
| Trueline Beverage Company Limited | Manufacturing | 2020 |
| Trumps Farm Storage & Locations Ltd | Transport & logistics | 2021 |
| Trust Hotel Reservations Limited | Hospitality | 1999 |
| Trustwell Designs Ltd. | Construction | 2020 |
| TRY Blue Ltd | Construction | 2017 |
| TS Smart Cleaning Limited | Administrative & support | 2024 |
| Tsbt Limited | Real estate | 2024 |
| Tudor Court (North Park) Management Company Limited | Households | 2004 |
| Tuition Wise Ltd | Other services | 2022 |
| Tulipa (Chipperfield) Management Company Limited | Households | 2021 |
| Tunmers Management Limited | Real estate | 1982 |
| Turtle Clips Limited | Manufacturing | 2021 |
| Tussl Ltd | Professional & scientific | 2026 |
| Twcb Ltd | Information & communication | 2018 |
| Tweed and Tartan Retail Ltd | Wholesale & retail | 2025 |
| Twenty Four Frames Ltd | Information & communication | 2023 |
| Twenty Seven Group Ltd | Financial services | 2023 |
| Twist 'N' Shout Ltd | Other services | 2006 |
| Two Flints Brewing Ltd | Manufacturing | 2022 |
| Two Rivers Accounting Services Limited | Professional & scientific | 2015 |
| Two Seas Property Ltd | Financial services | 2020 |
| TWT (London) Limited | Other services | 2012 |
| Tynan D'Arcy Limited | Professional & scientific | 1991 |
| Typden Limited | Information & communication | 2016 |
| Uche RUM Ltd | Wholesale & retail | 2021 |
| Uclass Limited | Information & communication | 2008 |
| UK Ghana Shipping Ltd | Transport & logistics | 2024 |
| UK National Properties Ltd | Real estate | 2020 |
| UK Parking Limited | Real estate | 2012 |
| UK Property Solutions (West WEY) Limited | Construction | 2020 |
| UK Tenda Co. Ltd | Wholesale & retail | 2020 |
| Ultimate Exec Limited | Other services | 2025 |
| Ultraplush Limited | Professional & scientific | 1987 |
| Ultratec Tuning Limited | Information & communication | 2022 |
| Umber's Beauty Bar Ltd | Other services | 2023 |
| Umber's Properties Ltd | Real estate | 2025 |
| Undercover Books Limited | Information & communication | 2015 |
| Undercover Publishing Limited | Information & communication | 2015 |
| Unique Care Windsor Ltd | Health & social care | 2025 |
| Unique Roofing & Building Ltd | Construction | 2024 |
| Unique Roofing & Guttering Ltd | Construction | 2025 |
| Unisolo Group Limited | Construction | 2024 |
| United Homes Limited | Construction | 2016 |
| United Internaltional (PVT) Limited | Wholesale & retail | 2024 |
| United Universal (PVT) Limited | Wholesale & retail | 2024 |
| Unwind Yoga Studio Limited | Other services | 2019 |
| Upper Meadow (Gerrards Cross) Management Company Limited | Households | 2007 |
| Upton House Limited | Wholesale & retail | 2009 |
| Upton Park Management (Slough) Limited | Households | 1972 |
| Uranium Computing Limited | Information & communication | 1990 |
| Urban & City Ltd | Construction | 2016 |
| Urban Designs & Developments (Wokingham) Limited | Construction | 2008 |
| Urban Wholesalers Limited | Wholesale & retail | 2013 |
| Urban Wholesalers Properties Ltd | Real estate | 2024 |
| Urbanmoon Properties Limited | Real estate | 2026 |
| Urbanova Ltd | Construction | 2025 |
| Urbansuite Lago Ltd | Wholesale & retail | 2025 |
| Urbansuite Windsor Ltd | Wholesale & retail | 2021 |
| Usha Sharma Medical Limited | Health & social care | 2021 |
| Usman & Co Ltd | Professional & scientific | 2004 |
| Usman Iqbal Ltd | Administrative & support | 2023 |
| Uttam & Diya Ltd | Real estate | 2024 |
| Uubc Ltd | Other services | 2020 |
| Uunify Limited | Information & communication | 2019 |
| Uwajh Jewels Ltd | Manufacturing | 2026 |
| UZ MI Records Ltd | Information & communication | 2018 |