| UK Safe Access Solutions Limited | Construction | 2025 |
| UK Self Protection Ltd | Education | 2021 |
| UK Splashbacks Limited | Wholesale & retail | 2009 |
| UK Staffing Solutions Ltd | Administrative & support | 2025 |
| UK Steel Solutions Ltd | Construction | 2019 |
| UK Tankers Ltd | Water & waste | 2025 |
| UK Technoserve Limited | Information & communication | 2019 |
| UK Tracing Limited | Administrative & support | 2025 |
| UK Vehicle Sales Ltd | Wholesale & retail | 2001 |
| UK Waste Holdings Ltd | Water & waste | 2025 |
| UK2020 Limited | Households | 2020 |
| Uknetmonitor Limited | Information & communication | 2005 |
| Ukpricecrusher Ltd | Wholesale & retail | 2026 |
| UKR General Trading Limited | Wholesale & retail | 2023 |
| UKS Tax Advisors Limited | Professional & scientific | 2016 |
| Uktek Ltd | Manufacturing | 2025 |
| Ulcombe Fibre CIC | Information & communication | 2024 |
| Uljana Limited | Wholesale & retail | 2012 |
| Ultimate Clothing Limited | Manufacturing | 2002 |
| Ultimate Cloud Ltd | Professional & scientific | 1998 |
| Ultimate Driveway Solutions Ltd | Construction | 2019 |
| Ultimate Kayaks Limited | Wholesale & retail | 2009 |
| Ultime Care Limited | Health & social care | 2024 |
| Ultra Soft Water Softeners Ltd | Professional & scientific | 2021 |
| Ultra Vision Glazing Systems Ltd | Construction | 2021 |
| Umiak Ltd | Professional & scientific | 2023 |
| UNA ST Ives Homes Limited | Real estate | 2014 |
| Unblurred Signs & Graphics Ltd | Professional & scientific | 2025 |
| Uncommon Creative Studio Holding Limited | Professional & scientific | 2017 |
| Uncommon Creative Studio Limited | Professional & scientific | 2021 |
| Uncommon Experience Studio Limited | Professional & scientific | 2021 |
| Under the Clock (Kent) Ltd | Health & social care | 2018 |
| Under the Tree Consulting Ltd | Health & social care | 2019 |
| Underdog to Owner Ltd | Information & communication | 2026 |
| Underlyn Lane LLP | | 2017 |
| Underwood Carpenter Limited | Professional & scientific | 2000 |
| Undisputed Lock & Glazing Services Ltd | Construction | 2024 |
| Unearthed Geotechnical Associates Ltd | Professional & scientific | 2022 |
| Uniacre Limited | Administrative & support | 2005 |
| Unicorn Electrical Limited | Professional & scientific | 1993 |
| Unifee Limited | Financial services | 2025 |
| Unified Commerce Ltd | Wholesale & retail | 2024 |
| Unify Telecoms Ltd | Information & communication | 2019 |
| Union Enterprises Limited | Administrative & support | 2018 |
| Union Group Holdings Limited | Financial services | 2016 |
| Union Group Limited | Financial services | 2017 |
| Union Homes Limited | Real estate | 2014 |
| Union International Limited | Other services | 2017 |
| Union Legal Limited | Professional & scientific | 2023 |
| Union Money Limited | Financial services | 2016 |
| Union OIL Limited | Wholesale & retail | 2023 |
| Union Properties Limited | Real estate | 2017 |
| Union Property Group Limited | Construction | 2016 |
| Union Rise Ltd | Transport & logistics | 2024 |
| Union Street RTM Company Limited | Households | 2009 |
| Union Travel Limited | Administrative & support | 2017 |
| Uniq Snowsports Limited | Administrative & support | 2020 |
| Uniq X Global Limited | Administrative & support | 2024 |
| UNIQ3 Projects Ltd | Construction | 2022 |
| Unit Engineering Simulators Ltd | Professional & scientific | 2026 |
| United Cars (Kent) Ltd | Extraterritorial | 2025 |
| United Consultancy Ltd | Real estate | 2003 |
| UNITRANSPORT2017 Limited | Transport & logistics | 2017 |
| Unity Coworking Limited | Administrative & support | 2007 |
| Unity Parties Limited | Hospitality | 2019 |
| Universal Dynamic Ltd | Construction | 2018 |
| Universal Supplies Group Ltd | Other services | 2019 |
| Universal Traders London Ltd | Wholesale & retail | 2011 |
| Unleash Yourself With Gladness CIC | Education | 2021 |
| Unleashed PR Limited | Wholesale & retail | 2005 |
| Unlimited Courage Limited | Other services | 2025 |
| Unlock, for People With Criminal Records | Other services | 1999 |
| Unmea Ltd | Construction | 2022 |
| Unravelled Games Ltd | Information & communication | 2024 |
| UP 2 Nine Premier Ltd | Wholesale & retail | 2026 |
| UP2 Mart Ltd | Wholesale & retail | 2025 |
| Upfront Television Limited | Professional & scientific | 1991 |
| Uplift Elevators Ltd | Manufacturing | 2024 |
| Upmart News Agent Ltd | Wholesale & retail | 2012 |
| Upper Medway Farms Ltd. | Agriculture & fishing | 1997 |
| Upper Road Limited | Extraterritorial | 2014 |
| Upper Tape Limited | Other services | 1987 |
| Uptima Solutions Ltd | Administrative & support | 2012 |
| UPZ and Downz Community Interest Company | Health & social care | 2010 |
| Urban Blue BUS (Maidstone) Limited | Health & social care | 2013 |
| Urban Cooling North Ltd | Construction | 2025 |
| Urban Lounge Golf Ltd | Arts & recreation | 2025 |
| Urban Mosaics Ltd | Construction | 2019 |
| Urban Nest Property Ltd | Real estate | 2019 |
| Urban Steel Services Limited | Construction | 2018 |
| Urbane Interior Designs Limited | Construction | 2024 |
| Urbase Ltd | Real estate | 2019 |
| Urbo Trading Ltd | Wholesale & retail | 2022 |
| Urenna Chekwas Fashion Limited | Wholesale & retail | 2025 |
| Ursu Transportation Ltd | Transport & logistics | 2021 |
| Ursus SPV Limited | Information & communication | 2024 |
| Urunn Limited | Information & communication | 2024 |
| Urus Transport Ltd | Transport & logistics | 2022 |
| Ushad Retail Limited | Wholesale & retail | 2026 |
| USP Training Limited | Professional & scientific | 2022 |