| UK Wholesale Direct Ltd | Information & communication | 2005 |
| UK Xtoworld Ltd | Information & communication | 2022 |
| Uklfi Limited | Other services | 2010 |
| Ukpa Trading Ltd | Information & communication | 2019 |
| Ukraine Freedom Company Ltd | Health & social care | 2022 |
| Ukrenovate Ltd | Construction | 2021 |
| Uks&V Holdings Limited | Professional & scientific | 2007 |
| Uks&V Ltd. | Information & communication | 1986 |
| Ultimate Media Group Limited | Information & communication | 2019 |
| Ultimate Media Systems Ltd | Information & communication | 2024 |
| Ultivar Group Ltd | Wholesale & retail | 2026 |
| Ultivar Ltd | Wholesale & retail | 2026 |
| Ultivar Supplies Ltd | Wholesale & retail | 2026 |
| Ultra Plastics Ltd | Manufacturing | 2006 |
| Ultra Sonic Anti Fouling Ltd | Wholesale & retail | 2007 |
| Ultramarine Services Limited | Manufacturing | 2016 |
| UM Marine Training Ltd | Education | 2025 |
| Umaria South Ltd | Real estate | 2022 |
| Umbhold Limited | Financial services | 2025 |
| Umbrella Four Ltd | Real estate | 2021 |
| Umbrella Property Solutions (Wessex) Ltd | Manufacturing | 2026 |
| Umbrella Zone Limited | Administrative & support | 2022 |
| Umer Farooq Ltd | Wholesale & retail | 2025 |
| Un-Selective UK Limited | Wholesale & retail | 2025 |
| Unbeatable Automotive Ltd | Wholesale & retail | 2023 |
| Unbranded Trading Co Ltd. | Wholesale & retail | 2025 |
| Uncharted Travel Limited | Administrative & support | 2026 |
| Uncle BOB Media Ltd | Information & communication | 2014 |
| Uncrewed Technologies Ltd | Information & communication | 2015 |
| Underhill Traders Limited | Real estate | 2018 |
| Undiluted Spirit Limited | Wholesale & retail | 2018 |
| Undine Global Ltd | Wholesale & retail | 2022 |
| Unfiltered Women Ltd | Administrative & support | 2024 |
| Unicard Limited | Information & communication | 2003 |
| Unified Design Group Ltd | Professional & scientific | 2021 |
| Unified Quantum Information Field (UIF) Technologies Ltd | Professional & scientific | 2025 |
| Unified Tech Holdings Ltd | Extraterritorial | 2021 |
| Union Gate Ltd | Wholesale & retail | 2025 |
| Union MSC Limited | Wholesale & retail | 2018 |
| Uniprint Limited | Professional & scientific | 2012 |
| Unique Accountants Ltd | Professional & scientific | 2017 |
| Unique Aluminium Decks Ltd | Construction | 2021 |
| Unique Commercial Investments Ltd | Real estate | 2016 |
| Unique Commercial Projects Ltd | Real estate | 2024 |
| Unique Courier Services Limited | Transport & logistics | 2023 |
| Unique Fire and Security Ltd | Public administration | 2012 |
| Unique Fire Door Services Limited | Water & waste | 2024 |
| Unique Garden Rooms Limited | Construction | 2021 |
| Unique Group (Southern) Ltd | Other services | 2016 |
| Unique Group (SW) Ltd | Information & communication | 2016 |
| Unique Interiors (Southern) Limited | Construction | 2003 |
| Unique Outdoor Living Group Limited | Construction | 2021 |
| Unique Pavestones Ltd | Administrative & support | 2021 |
| Unique Premium Products Ltd | Wholesale & retail | 2020 |
| Unique Prestige Cars Limited | Wholesale & retail | 2012 |
| Unique Prestige Taxis Limited | Transport & logistics | 2016 |
| Unique Renewable Energy Ltd | Information & communication | 2018 |
| Unique Sealants Ltd | Construction | 2010 |
| Unique Vehicle Body Repairs Ltd | Wholesale & retail | 2018 |
| Uniserve Poole Ltd | Administrative & support | 2014 |
| Unison MKT Ltd | Manufacturing | 2024 |
| Unit C Outlook Management Limited | Real estate | 2024 |
| Unit D Outlook Management Limited | Real estate | 2024 |
| Unitatis Limited | Real estate | 2021 |
| Unite Electrical Contracting Ltd | Construction | 2024 |
| Unitecx Limited | Education | 2026 |
| United European Airlines Limited | Administrative & support | 2006 |
| United Hi-Tech UK Limited | Professional & scientific | 2005 |
| United Kingdom Waterski Racing Limited | Other services | 2024 |
| Unitproductionpro Ltd | Manufacturing | 2024 |
| Units 1-6 Brook Road Management Limited | Households | 2011 |
| Unity Exchange Ltd | Professional & scientific | 2025 |
| Unity Living Estates Ltd | Real estate | 2025 |
| Univenta Ltd | Wholesale & retail | 2025 |
| Universal Cleaning Limited | Other services | 1984 |
| Universal Commercial Enterprises Ltd | Wholesale & retail | 2026 |
| Universal Tokenized Technologies Ltd | Information & communication | 2023 |
| Universal-Elecricals Limited | Wholesale & retail | 2016 |
| Univro Ltd | Financial services | 2025 |
| Unlay Media Limited | Information & communication | 2022 |
| Unleashed Apparel Limited | Wholesale & retail | 2016 |
| Unlock Capital Ltd | Financial services | 2026 |
| Unlock Potential Limited | Information & communication | 2014 |
| Unprototyped Limited | Information & communication | 2017 |
| UNR2911 Ltd | Wholesale & retail | 2025 |
| Unrivalled Security Services Ltd | Administrative & support | 2013 |
| UNS Holdings Ltd | Financial services | 2019 |
| Unstick Limited | Information & communication | 2002 |
| Unstoppable Media Limited | Information & communication | 2018 |
| UON BR Ltd | Wholesale & retail | 2025 |
| UP Top Roofing Specialists Ltd | Construction | 2021 |
| UP Top Scaffolding Ltd | Construction | 2023 |
| Upaya Ltd | Wholesale & retail | 2017 |
| UPC Cars Limited | Wholesale & retail | 2020 |
| Uplift Planning and Property Limited | Professional & scientific | 2025 |
| Upmake Ltd | Arts & recreation | 2025 |
| Upperwalk Estates Ltd | Construction | 2005 |
| Upright Trading Ltd | Wholesale & retail | 2020 |
| Uprise Corporations Ltd | Wholesale & retail | 2025 |
| Uprising Software Ltd | Information & communication | 2013 |