| Ultimate Packaging Limited | Administrative & support | 2026 |
| Ultimate Screed Solution Ltd | Construction | 2013 |
| Ultra Premium Brands Limited | Wholesale & retail | 2003 |
| Ultra Rendering Company Ltd | Construction | 2019 |
| Ultra Tech Consulting Limited | Information & communication | 2021 |
| ULTRA-FIT-4U Limited | Wholesale & retail | 2025 |
| Ultranetix Ltd | Construction | 2026 |
| UM Haulage Ltd | Transport & logistics | 2025 |
| Umahacademy Limited | Education | 2025 |
| Umair Property Investments Limited | Real estate | 2026 |
| Umar and Sons Limited | Wholesale & retail | 2025 |
| Umar Farooq Photography Ltd | Professional & scientific | 2018 |
| Umar Property Ltd | Real estate | 2024 |
| Umeed LTN Ltd | Wholesale & retail | 2026 |
| Umer Well Ltd | Wholesale & retail | 2025 |
| Umgl Ltd | Real estate | 2024 |
| Ummah Consulting Limited | Professional & scientific | 2023 |
| Ummah Decorators Limited | Construction | 2025 |
| UMU ADA Okpu Mbaise in UK | Other services | 2023 |
| UN MAX DE Productions Limited | Professional & scientific | 2024 |
| UNA Commerce Limited | Wholesale & retail | 2026 |
| Unanimote Limited | Extraterritorial | 2011 |
| Unbound LND Limited | Education | 2025 |
| Unchained Finance Group Ltd | Financial services | 2023 |
| Uncia Limited | Information & communication | 2022 |
| Uncle SAM Transport Limited | Transport & logistics | 2026 |
| Unfilteredfertility Ltd | Education | 2025 |
| UNI Finder Ltd | Professional & scientific | 2018 |
| UNI Star International UK Ltd | Manufacturing | 2023 |
| Unibuild Engineering Services Limited | Professional & scientific | 2025 |
| Unicorn (Residential) Limited | Real estate | 2010 |
| Unicorn Brands Ltd | Wholesale & retail | 2020 |
| Uniexperts Limited | Information & communication | 2020 |
| Unified Events Ltd | Other services | 2017 |
| Unigent Consult Ltd | Administrative & support | 2020 |
| Unigent Logistics and Supplies Ltd | Wholesale & retail | 2025 |
| Unikat Limited | Other services | 2021 |
| Unimatrix Zero Limited | Professional & scientific | 2007 |
| Union Cars Luton Ltd | Transport & logistics | 2026 |
| Uniqo Contractors Ltd | Construction | 2019 |
| Unique BAU Limited | Construction | 2021 |
| Unique Consultancy & Services Ltd | Financial services | 2025 |
| Unique Detail Limited | Other services | 1999 |
| Unique Items Ltd | Wholesale & retail | 2025 |
| Unique Prime-Cleaning Ltd | Administrative & support | 2025 |
| Unique Rivers Ltd | Real estate | 2018 |
| Unique Therapy and Counselling Services Ltd | Health & social care | 2019 |
| Unique Transport Logistics Ltd | Transport & logistics | 2019 |
| Unique View Enterprises Limited | Construction | 1990 |
| Uniqverse Ltd | Real estate | 2025 |
| Unisense Property Limited | Real estate | 2019 |
| Unit 723 Luton Building Management Company Limited | Real estate | 2011 |
| Unit D Abbeygate Ltd | Real estate | 2024 |
| Unite Catering Services Ltd | Manufacturing | 2022 |
| Unite Facilities Services Limited | Public administration | 2021 |
| United 3 Star Limited | Wholesale & retail | 2024 |
| United Courier's Services Ltd | Transport & logistics | 2026 |
| United Energy Limited | Construction | 2025 |
| United Hub Razom CIC | Education | 2025 |
| United Naturals Ltd | Wholesale & retail | 2025 |
| United Solution Security Limited | Other services | 2019 |
| United UK Vision Ltd | Hospitality | 2024 |
| Unity 4 Living Ltd | Health & social care | 2025 |
| Unity Care Services Ltd | Public administration | 2025 |
| Unity Horizons CIC | Health & social care | 2024 |
| Unity Pads Ltd | Real estate | 2023 |
| Unitycollectables Ltd | Wholesale & retail | 2023 |
| Univers Plastering Limited | Construction | 2016 |
| Universal Distributors Ltd | Wholesale & retail | 2023 |
| Universal Galaxy Hire Cars Ltd | Administrative & support | 2021 |
| Universal Heaven Ltd | Wholesale & retail | 2021 |
| Universal Love LL Ltd | Other services | 2024 |
| Universal Mechanic Ltd | Wholesale & retail | 2025 |
| Universal Panels Ltd | Wholesale & retail | 2024 |
| Universal Parking Enforcement Limited | Transport & logistics | 2020 |
| Universal Pest Control (Home Counties) Ltd | Professional & scientific | 2009 |
| Universal Properties Solution Ltd | Real estate | 2020 |
| Universal Property Estates Limited | Real estate | 2007 |
| Universal Recovery Ltd | Transport & logistics | 2023 |
| Universal Safety Consultants Limited | Information & communication | 1994 |
| Universal Services (EU) Ltd | Transport & logistics | 2012 |
| Universal Services Solutions Ltd | Administrative & support | 2026 |
| Universal Shoes Limited | Wholesale & retail | 2006 |
| Universal Solutions Ltd | Administrative & support | 2024 |
| Universal Sound Hire Ltd | Arts & recreation | 2024 |
| Universal Television & Media Ltd | Professional & scientific | 2012 |
| University Campus Milton Keynes Limited | Education | 2017 |
| University of Bedfordshire Enterprises Limited | Education | 1990 |
| Unix Logistics Limited | Transport & logistics | 2022 |
| Unlimited Constructions Ltd | Construction | 2019 |
| Unlimited Royalty Ltd | Information & communication | 2021 |
| Unlimity Ltd | Professional & scientific | 2024 |
| UNO Technologies Limited | Information & communication | 2025 |
| Untouchable Carwash Ltd | Administrative & support | 2023 |
| Untouchable Promotions Ltd | Arts & recreation | 2013 |
| UP Steel Limited | Construction | 2025 |
| Update Web Advertising Limited | Wholesale & retail | 2019 |
| Updrift Ltd | Professional & scientific | 2019 |
| Uplifting Care Services Ltd | Health & social care | 2024 |
| Upper Berkeley Group Ltd | Real estate | 2025 |