| TUI Travel Overseas Holdings Limited | Professional & scientific | 2003 |
| TUI UK Limited | Administrative & support | 1993 |
| TUI UK Retail Limited | Administrative & support | 1979 |
| TUI UK Transport Limited | Other services | 1971 |
| Tuition Central Limited | Education | 2024 |
| Tuition Experts Ltd | Professional & scientific | 2015 |
| Tulip Accountants Limited | Professional & scientific | 2022 |
| Tunesto Ltd | Health & social care | 2025 |
| Tupaa Ltd | Wholesale & retail | 2026 |
| Tuppers Company Limited | Health & social care | 2018 |
| Turag Clothing Limited | Wholesale & retail | 2020 |
| Turcu Express Ltd | Transport & logistics | 2025 |
| Turkish Barber Marsh Ltd | Other services | 2023 |
| Turna Properties Ltd | Real estate | 2021 |
| Turnbull Industries Ltd | Manufacturing | 2023 |
| Turner & Knight Ltd | Construction | 2024 |
| Turnerstone Consulting Limited | Professional & scientific | 2024 |
| Turnika Avram Cleaning Ltd | Construction | 2022 |
| Turnkey Digital Ltd | Professional & scientific | 2021 |
| Turtleson International Limited | Wholesale & retail | 2019 |
| Turvey Capital LLP | | 2026 |
| Turvey House Limited | Real estate | 2020 |
| Tusem Ltd | Professional & scientific | 2006 |
| Tushiya Technology Group Limited | Information & communication | 2018 |
| Tuskar Financial Consultancy Limited | Professional & scientific | 2021 |
| Tustone Technical Services Limited | Information & communication | 2015 |
| Tutor ED Ltd | Education | 2025 |
| Tutorbook Ltd | Education | 2021 |
| TVK Private Ltd | Hospitality | 2024 |
| Tvntrade Ltd | Wholesale & retail | 2025 |
| TW Counselling and Education Ltd | Professional & scientific | 2016 |
| Twelve (UK) Limited | Transport & logistics | 2014 |
| Twelve by Twelve Limited | Wholesale & retail | 2020 |
| Twelve by Twelve Properties Limited | Real estate | 2024 |
| Twenty Two Brokers Limited | Financial services | 2025 |
| TWENTY15 Investment Limited | Construction | 2015 |
| TWENTY19 Investments Limited | Wholesale & retail | 2018 |
| TWENTY24 Investments Limited | Real estate | 2024 |
| TWENTY47 Logistics Limited | Transport & logistics | 2019 |
| TWENTY4SEVEN Online Ltd | Wholesale & retail | 2024 |
| TWENTYFOUR-7 Heating & Plumbing Ltd | Construction | 2016 |
| Twentynine Barbers Limited | Other services | 2026 |
| Twin Group Ltd | Construction | 2020 |
| Twin Wholesale Group Ltd | Wholesale & retail | 2025 |
| Twinings Security and Consultancy Limited | Administrative & support | 2013 |
| Twinjet Aircraft Sales (UK) Limited | Wholesale & retail | 2007 |
| Twinklepro Ltd | Administrative & support | 2025 |
| Twinning Hair & Beauty Ltd | Other services | 2023 |
| Twins Car Sales Limited | Wholesale & retail | 2026 |
| Twirl Ltd | Hospitality | 2026 |
| Two Brothers Halal Limited | Wholesale & retail | 2025 |
| Two by Four Consultancy Ltd | Real estate | 2019 |
| Two Coins Tattoo Ltd | Other services | 2023 |
| Two Grains Limited | Real estate | 2025 |
| Two Side Studios Ltd | Information & communication | 2023 |
| Two Steaks Ltd | Hospitality | 2021 |
| Two Tales Creative Limited | Information & communication | 2011 |
| Twynersh Fishing Complex Ltd | Arts & recreation | 2002 |
| TY Haus Limited | Real estate | 2017 |
| TYK Garage Ltd | Wholesale & retail | 2022 |
| Tylc Limited | Real estate | 2024 |
| Tynellis Ltd | Wholesale & retail | 2026 |
| TYP International Limited | Arts & recreation | 2017 |
| Tyre & Parts Buyer Ltd. | Extraterritorial | 2008 |
| Tyre Centre Luton Ltd | Wholesale & retail | 2024 |
| Tyre Times Ltd | Wholesale & retail | 2026 |
| Tyre Treads 247 Ltd | Wholesale & retail | 2026 |
| Tyre Treads Ltd | Wholesale & retail | 2016 |
| Tyred and Exhausted Auto Centres Limited | Wholesale & retail | 2004 |
| Tyres Direct 247 Limited | Wholesale & retail | 2026 |
| Tyst Ltd | Construction | 2025 |
| Tythe Road Management Limited | Households | 1982 |
| Tytus Deliveries Ltd | Transport & logistics | 2014 |
| TZ Asset Management Ltd | Hospitality | 2025 |
| TZ Consulting and Managed Services Ltd | Real estate | 2022 |
| TZ Ductwork Ltd | Construction | 2018 |
| U & G Limited | Other services | 2018 |
| U & SA Ltd | Wholesale & retail | 2024 |
| U 007 Limited | Hospitality | 2015 |
| U and a Locums Limited | Health & social care | 2012 |
| U Trim Ltd | Wholesale & retail | 2026 |
| U&A Perfumex Ltd | Wholesale & retail | 2025 |
| U&F Investment Ltd | Real estate | 2025 |
| U&H Solutions Ltd | Real estate | 2025 |
| U-Turn in Life Skills Ltd | Health & social care | 2024 |
| U.J Support Services Limited | Information & communication | 2017 |
| UA Distributor Ltd | Wholesale & retail | 2026 |
| UA Electrical Services Ltd | Manufacturing | 2021 |
| UA Fashionstudio Ltd | Wholesale & retail | 2025 |
| UA MMA CIC | Arts & recreation | 2020 |
| UA Motors Ltd | Wholesale & retail | 2025 |
| UA Properties Holding Ltd | Real estate | 2024 |
| Ua.Sh Limited | Other services | 2023 |
| UAE Consultancy Ltd | Administrative & support | 2017 |
| UAT 24/7 Ltd | Transport & logistics | 2023 |
| UB Brother Ltd | Hospitality | 2020 |
| UB Traders Ltd | Wholesale & retail | 2026 |
| Ubantu (WE ARE One) Community Interest Company | Education | 2024 |
| Ubbad Promotions Limited | Professional & scientific | 2015 |
| Ubiquity Consulting Limited | Information & communication | 2017 |