| Treerebral Ltd | Administrative & support | 2024 |
| Treets Limited | Wholesale & retail | 2013 |
| Trelawney Court Management (Bournemouth) Limited | Households | 2005 |
| Trelgajo Services Limited | Professional & scientific | 2012 |
| Trent Consulting Limited | Information & communication | 2025 |
| Trentwilliams Ltd | Information & communication | 2013 |
| Tres Chorizos Limited | Information & communication | 2025 |
| Triad Developments Limited | Construction | 2015 |
| Triangled Ltd | Information & communication | 2018 |
| Tribes Travel Limited | Administrative & support | 1998 |
| Tricia Hayes Consultancy Limited | Professional & scientific | 2024 |
| Trident Coatings Limited | Administrative & support | 2006 |
| Trinity Close (Wareham) Limited | Households | 1968 |
| Trinity Flats Management Limited | Households | 1983 |
| Tristan Hutton Music Limited | Arts & recreation | 2025 |
| Tristram Commercial Developments Limited | Real estate | 2005 |
| Tristram Securities Limited | Extraterritorial | 2005 |
| Tritest Limited | Information & communication | 2018 |
| Triton Land Ltd | Real estate | 2020 |
| Triton Scaffolding Limited | Construction | 1999 |
| Tronicblade Limited | Administrative & support | 2011 |
| Troton Consulting Limited | Professional & scientific | 1996 |
| TRT Worldwide Engineering Ltd | Manufacturing | 2025 |
| Trucut Holdings Ltd | Financial services | 2023 |
| Trucut Ltd | Wholesale & retail | 2015 |
| True & Fair Accountants Ltd | Professional & scientific | 2020 |
| True Cloud Solutions Limited | Information & communication | 2023 |
| True North Consulting Ltd | Administrative & support | 2021 |
| True North Holdings Limited | Professional & scientific | 2025 |
| True Real Estate Invest Ltd | Real estate | 2016 |
| Truehealthx Limited | Professional & scientific | 2025 |
| Trupool UK Limited | Manufacturing | 2007 |
| Truscapes Limited | Administrative & support | 2019 |
| Trust Healthcard Limited | Health & social care | 2016 |
| Trusted Builder Dorset Ltd | Construction | 2025 |
| Trusted Datawesome Consulting Ltd | Information & communication | 2023 |
| Trusted Plumber Limited | Construction | 2022 |
| Trylexo Limited | Extraterritorial | 2018 |
| TS Flooring Ltd | Wholesale & retail | 2020 |
| TSD Projects Limited | Information & communication | 2010 |
| TSL Future Limited | Transport & logistics | 2016 |
| TSW Catering Limited | Hospitality | 2018 |
| Ttamsenoj Limited | Information & communication | 2015 |
| TTH Limited | Other services | 1996 |
| Tthcurzon Relocation Limited | Other services | 2015 |
| Tubbs Holdings Limited | Real estate | 2023 |
| Tuned Services Limited | Arts & recreation | 2002 |
| Turner Consulting Limited | Professional & scientific | 2026 |
| Turner Urology Limited | Health & social care | 2015 |
| Turnit Solutions Ltd | Information & communication | 2014 |
| Turnkey Website Solutions Limited | Information & communication | 2013 |
| Turnparts Engineering Limited | Manufacturing | 2009 |
| Turnparts Holdings Limited | Financial services | 1980 |
| TVR Consulting Limited | Information & communication | 2025 |
| TW Plastic Coatings Ltd | Manufacturing | 2008 |
| Twinn Consulting Limited | Information & communication | 2003 |
| Two Fields Zakros Ltd | Wholesale & retail | 2017 |
| Two Rivers Mill Limited | Manufacturing | 2010 |
| Two Wolves Design Limited | Other services | 2020 |
| TXI Satcom Limited | Extraterritorial | 2023 |
| Tyre and Autocare Ltd | Wholesale & retail | 2024 |
| Tyremarx Limited | Wholesale & retail | 2020 |
| Tyrrell Group Limited | Construction | 2001 |
| Tyrrell Holdings Limited | Construction | 1985 |
| U Certify Ltd | Information & communication | 2015 |
| Ufhn Holdings Ltd | Financial services | 2019 |
| Ufhn Ltd | Construction | 2004 |
| Ujas Code Ltd | Information & communication | 2025 |
| Ujcs Limited | Information & communication | 2022 |
| UJX Ltd | Information & communication | 2024 |
| UK ADC Ltd | Other services | 2016 |
| UK Aircraft Engineers Limited | Manufacturing | 2018 |
| UK Country Ltd | Wholesale & retail | 2023 |
| UK Mapping Limited | Administrative & support | 2009 |
| UK One Consulting Limited | Professional & scientific | 2005 |
| UK Pest Ltd | Water & waste | 2009 |
| UK Small Caps Limited | Information & communication | 2023 |
| Ukraine UK AID CIC | Wholesale & retail | 2026 |
| Ultra BEE Health Ltd | Wholesale & retail | 2014 |
| Ultran Ltd | Information & communication | 2019 |
| Ulyett Consultants Ltd | Professional & scientific | 2026 |
| Ulyett Electrical Services Ltd | Construction | 2022 |
| Umar Khan Tech Limited | Information & communication | 2026 |
| Umbras Operations Ltd | Other services | 2020 |
| Underfloor Store Ltd | Wholesale & retail | 2015 |
| Underwater Technical Solution Limited | Professional & scientific | 2026 |
| Unicorn Online Marketing Limited | Information & communication | 2017 |
| Unify Learning & Development Limited | Professional & scientific | 2021 |
| Uniprep Limited | Administrative & support | 2000 |
| Unique Civil Engineering and Plant Hire Ltd | Construction | 2023 |
| Unique Drains Ltd | Water & waste | 2024 |
| Unique Experts Ltd | Administrative & support | 2020 |
| Unitas Inns Ltd | Hospitality | 2025 |
| United Fencing Limited | Administrative & support | 2013 |
| United Fencing Supplies Limited | Wholesale & retail | 2018 |
| United Mechanical FM Limited | Energy | 2025 |
| United Mechanical Ltd | Energy | 2010 |
| United Powder Coating Limited | Manufacturing | 2016 |
| United Restaurants Limited | Extraterritorial | 2014 |
| Uniton Services Limited | Information & communication | 2017 |