| UK Poulos International Horticultural Products Ltd | Administrative & support | 2021 |
| UK Property Compliance Ltd | Professional & scientific | 2019 |
| UK Property LET Ltd | Real estate | 2024 |
| UK Puzzle Removals Ltd | Transport & logistics | 2017 |
| UK SJH International Chemical Group Limited | Manufacturing | 2021 |
| UK Sports Pics Ltd | Professional & scientific | 2013 |
| UK Study NOW Ltd | Education | 2026 |
| UK Tairui Trade Co., Ltd | Wholesale & retail | 2025 |
| UK Tyre Wholesalers Ltd | Wholesale & retail | 2019 |
| UK Voltix Electrical Ltd | Construction | 2026 |
| UK4HOME Ltd | Other services | 2008 |
| UKA Line Ltd | Transport & logistics | 2025 |
| Ukcoorperate Ltd | Wholesale & retail | 2026 |
| Ukcraftfairs Ltd | Information & communication | 2012 |
| Ukita Food Ltd | Wholesale & retail | 2024 |
| Ukita Properties Ltd | Real estate | 2017 |
| Ukjam Onestop Consultancy Services Limited | Administrative & support | 2022 |
| Uktechforce Limited | Information & communication | 2013 |
| Ulbex UK Ltd | Construction | 2020 |
| Uley Masonry Limited | Construction | 2024 |
| Ullswater Flat Management Limited | Households | 2007 |
| Ultimate EC Ltd | Administrative & support | 2025 |
| Ultimate Glass Solutions Ltd | Construction | 2019 |
| Ultimate Heat Pumps Limited | Construction | 2023 |
| Ultimate Warrior Training Ltd | Other services | 2016 |
| Ultimate Yarns & Fibres Limited | Administrative & support | 2020 |
| Ultra Prime Cleaning Services Ltd | Administrative & support | 2021 |
| Ultrasound Centre Ltd | Health & social care | 2022 |
| Ultrawell Clinic Ltd | Health & social care | 2025 |
| Ultronergy Services Ltd | Construction | 2022 |
| UMA Inc Ltd | Information & communication | 2026 |
| Umargoods Ltd | Wholesale & retail | 2024 |
| Umbrella Link Ltd | Administrative & support | 2023 |
| Umiverse Ltd | Wholesale & retail | 2025 |
| UMM Amaanah Limited | Wholesale & retail | 2024 |
| UNAVU9 Ltd | Hospitality | 2026 |
| Underdog Kennels Ltd | Wholesale & retail | 2025 |
| Understanding Audio Ltd | Information & communication | 2017 |
| Understanding Strategies Ltd | Education | 2026 |
| Unfiltered London Limited | Information & communication | 2022 |
| UNI Lanka Retail Ltd | Wholesale & retail | 2020 |
| Uniacco Ltd | Hospitality | 2020 |
| Unic Coffee Ltd | Manufacturing | 2021 |
| Unicare Complex Care Specialist Ltd | Education | 2019 |
| Unicyp Investments Limited | Administrative & support | 2025 |
| Unieagle Limited | Health & social care | 2018 |
| Unifinco Holding Ltd | Financial services | 2020 |
| Unifix Ltd | Construction | 2025 |
| Unifybuilds Ltd | Construction | 2020 |
| Uniiway Exam Centre Limited | Education | 2023 |
| Union Capital Ltd | Construction | 2025 |
| Union City Media Limited | Information & communication | 2012 |
| Union Commerce UK Ltd | Wholesale & retail | 2024 |
| Union Hire and Sale Ltd | Administrative & support | 2008 |
| Union Professional Cleaning Services Ltd | Professional & scientific | 2012 |
| Unipharma Limited | Professional & scientific | 2014 |
| Unique Berlin Events Ltd | Administrative & support | 2006 |
| Unique Carpets South Harrow Limited | Wholesale & retail | 2014 |
| Unique Healthcare Solutions Ltd | Health & social care | 2022 |
| Unique Hospitality Ltd | Health & social care | 2025 |
| Unique Recruitement Limited | Administrative & support | 2026 |
| Unique Rings Ltd | Manufacturing | 2003 |
| Unique Sports Coaching Ltd | Education | 2022 |
| Uniquest Consulting Limited | Information & communication | 2010 |
| Unit Project CIC | Administrative & support | 2024 |
| Unitasty Ltd | Other services | 2019 |
| Unitebiz Consultancy Services Ltd | Information & communication | 2023 |
| Uniteck Limited | Construction | 2006 |
| United Benefits Services Limited | Professional & scientific | 2001 |
| United Efforts of Excellent Services (Uees) Ltd | Wholesale & retail | 2013 |
| United Mobiles PVT Limited | Wholesale & retail | 2026 |
| United Parasams Limited | Transport & logistics | 2025 |
| United Safe Care Limited | Administrative & support | 2008 |
| United Tech World Ltd | Information & communication | 2013 |
| United to Autism CIC | Education | 2025 |
| Unitek Limited | Professional & scientific | 2019 |
| Unitex Solutions Ltd | Financial services | 2022 |
| Unity Cargo Solutions Ltd | Transport & logistics | 2026 |
| Unity Cleaning Services Limited | Other services | 2020 |
| Unity Hub Croydon CIC | Hospitality | 2026 |
| Unity in Diversity Events & Productions Ltd | Arts & recreation | 2021 |
| Unity Psychology Limited | Education | 2022 |
| Universal Asset Management, Inc. (UK) Limited | Administrative & support | 2013 |
| Universal Business Group Limited | Wholesale & retail | 2024 |
| Universal ENGINEERS1313 Limited | Construction | 2023 |
| Universal Estates (Croydon) Limited | Real estate | 2007 |
| Universal Leisure London Limited | Hospitality | 2020 |
| UNK Properties Ltd | Real estate | 2024 |
| Unlimited Limit Limited | Information & communication | 2013 |
| Unveil London Ltd | Wholesale & retail | 2020 |
| UOA Limited | Information & communication | 2021 |
| UP Above Limited | Real estate | 2023 |
| UP to 11 Sound Ltd | Information & communication | 2012 |
| UPD Construction Limited | Construction | 2023 |
| Upfield Pharma Ltd | Wholesale & retail | 2016 |
| Upfolioplus Ltd | Information & communication | 2025 |
| Upfront and Personal Global Management Consultant Ltd | Hospitality | 2016 |
| Upminster Pharma Ltd | Wholesale & retail | 2026 |
| Upper Mannor Ltd | Administrative & support | 2024 |
| Upper Shirley Management Ltd | Real estate | 2026 |