| Ubizo Ltd | Wholesale & retail | 2021 |
| Ucability Limited | Professional & scientific | 2014 |
| Ufixu Physiotherapy Limited | Other services | 2006 |
| UK Blind & Curtain Installation Ltd | Construction | 2024 |
| UK Construction Support Limited | Administrative & support | 2017 |
| UK DOC Assist Ltd | Administrative & support | 2023 |
| UK Ella International Co., Ltd | Manufacturing | 2024 |
| UK Energy Initiative Limited | Energy | 2023 |
| UK Foam Limited | Wholesale & retail | 2015 |
| UK Jingle Bell Limited | Wholesale & retail | 2022 |
| UK Novatek Ltd | Information & communication | 2014 |
| UK Pothole Repairs Ltd | Construction | 2025 |
| UK Smart Security Ltd | Administrative & support | 2018 |
| UK Wills & Probate Ltd | Other services | 2019 |
| UK Ysair Technology Co., Ltd | Wholesale & retail | 2022 |
| Uk-China Education & Business Service Limited | Education | 2012 |
| Ukaus Services Ltd | Administrative & support | 2021 |
| Ukeducationservice Ltd | Education | 2011 |
| Ukorea Ltd | Wholesale & retail | 2021 |
| Ultra Roofcare Ltd | Construction | 2025 |
| Ultra Social Limited | Professional & scientific | 2012 |
| Umannix Computing Limited | Information & communication | 1988 |
| Umbria Taste Ltd | Hospitality | 2025 |
| Understanding AG UK Limited | Agriculture & fishing | 2025 |
| Understory Collective CIC | Other services | 2026 |
| Underwaterfilm Limited | Information & communication | 2006 |
| Unfaded LAB Ltd | Manufacturing | 2025 |
| Ungroup Limited | Information & communication | 2012 |
| UNI Corporation Limited | Other services | 2018 |
| Unicore London Limited | Construction | 2019 |
| Unicorn Crop Nutrition Co., Ltd. | Mining & quarrying | 2020 |
| Uniformerly Limited | Wholesale & retail | 2023 |
| Unikart Pinoy Cosmo Ltd | Hospitality | 2024 |
| Unilectric Ltd | Manufacturing | 2018 |
| Unilever Pension Trust Limited | Professional & scientific | 1935 |
| Unilever Superannuation Trustees Limited | Professional & scientific | 1972 |
| Unilever UK Limited | Manufacturing | 1937 |
| Unilever UK Pension Fund Trustees Limited | Professional & scientific | 1999 |
| Union Jack Properties Limited | Real estate | 2020 |
| Union of Truth CIC | Health & social care | 2022 |
| Unique Properties and Events Limited | Real estate | 2006 |
| Unique Selling Point Limited | Administrative & support | 2003 |
| Unit 4 London Ltd | Other services | 2022 |
| Unit One Store Limited | Transport & logistics | 2003 |
| United Kingdom Fertilizer Company Limited | Manufacturing | 2018 |
| United Peaks Ltd | Wholesale & retail | 2020 |
| United Travel Visa Limited | Administrative & support | 2007 |
| Unknown Brother Ltd | Professional & scientific | 2024 |
| Unleashed Solutions Limited | Information & communication | 2011 |
| Unlimited Money Limited | Other services | 2022 |
| Unmuddy Limited | Professional & scientific | 2018 |
| Unolabs Limited | Information & communication | 2021 |
| Unstoppable Properties Ltd | Real estate | 2020 |
| Unstoppable Training Studio Limited | Arts & recreation | 2025 |
| Untangling Ltd | Professional & scientific | 2008 |
| Until the Violence Stops | Health & social care | 2025 |
| Unwired Ventures Limited | Administrative & support | 2004 |
| Unwork.Com Limited | Administrative & support | 2010 |
| Unyted Limited | Information & communication | 2022 |
| UP the Game Limited | Information & communication | 2017 |
| Upholstery-London Ltd | Other services | 2021 |
| Uplands Risk Advisory Ltd | Professional & scientific | 2020 |
| UPM SYS Consulting Ltd | Wholesale & retail | 2023 |
| Upmark Ltd | Information & communication | 2025 |
| Upminster Management Limited | Households | 2025 |
| Upna Limited | Construction | 1998 |
| Upper Hampstead Walk Management Company Limited | Households | 1997 |
| Upper Sigma Limited | Other services | 2018 |
| Upwards Group Ltd | Information & communication | 2016 |
| UR Trading Ltd | Real estate | 2002 |
| Urban Capital Investments LLP | | 2016 |
| Urban Consulting Engineers Ltd | Professional & scientific | 2021 |
| Urban FOX Laboratory Limited | Information & communication | 2016 |
| Urban Meadows Limited | Administrative & support | 2006 |
| Urban Purpose Ltd | Professional & scientific | 2023 |
| Urban Structural Engineers Ltd | Professional & scientific | 2022 |
| Urbanfix.Services Limited | Construction | 2026 |
| Urethrotech Ltd | Manufacturing | 2007 |
| Urnammo UK Limited | Other services | 2014 |
| Useable IT Ltd | Information & communication | 2019 |
| USF Nominees Limited | Professional & scientific | 1932 |
| Utopia Creative Limited | Arts & recreation | 2016 |
| UX Research Workshop Ltd | Professional & scientific | 2021 |
| V J Aesthetics Ltd | Other services | 2021 |
| V-Brick Ltd | Wholesale & retail | 2025 |
| V. H. Willison Limited | Professional & scientific | 2010 |
| Va&T Ltd | Manufacturing | 2024 |
| VAE Victis Ltd | Construction | 2021 |
| Valedrive Valeauto Carvale Limited | Professional & scientific | 2018 |
| Vali Consulting Holdings Ltd | Information & communication | 2025 |
| Valyou Cars Limited | Wholesale & retail | 2020 |
| Van Weelden Consulting Limited | Professional & scientific | 2020 |
| Vanadium Build Limited | Construction | 2024 |
| Vanderquest Limited | Arts & recreation | 1978 |
| Vanguard Group Solutions Ltd | Information & communication | 2023 |
| Vanguard Luxe Property Ltd | Real estate | 2024 |
| Vanguard Management Limited | Professional & scientific | 2010 |
| Vanguard Metropolitan Limited | Real estate | 1927 |
| Vannda Partners Ltd | Information & communication | 2020 |
| Vapk Ltd | Wholesale & retail | 2025 |