| Tytal Lifts Ltd | Construction | 2017 |
| TZ Psychiatry Ltd | Health & social care | 2024 |
| U & KO Ltd | Wholesale & retail | 2011 |
| UAP Tech Limited | Information & communication | 2021 |
| Ubere Trading Limited | Manufacturing | 2014 |
| UCD Locums Limited | Administrative & support | 2014 |
| UD (Staines Road) Ltd | Real estate | 2016 |
| Ujeniuc Service Ltd | Construction | 2023 |
| UK Battery Repairs Ltd | Manufacturing | 2023 |
| UK Craft Beers Ltd | Wholesale & retail | 2025 |
| UK Driveways & Fencing Ltd | Administrative & support | 2017 |
| UK Eco Energy Limited | Administrative & support | 2011 |
| UK Electrical Services Ltd | Professional & scientific | 2026 |
| UK Errand Guru Limited | Other services | 2020 |
| UK Leak Detection Experts Ltd | Water & waste | 2025 |
| UK Levy Ltd | Education | 2015 |
| UK Light Store Ltd | Wholesale & retail | 2025 |
| UK Mastic MAN Limited | Construction | 2021 |
| UK Nails (Stevenage) Ltd | Other services | 2019 |
| UK OHL Ltd | Energy | 2026 |
| UK Products 247 Ltd | Wholesale & retail | 2025 |
| UK Residential Property Ltd | Construction | 2018 |
| UK Ventilation Systems Ltd | Construction | 2019 |
| UK Water Consultants Ltd | Professional & scientific | 2023 |
| UK22 Ltd | Information & communication | 2010 |
| Ukpermits & Visas Limited | Professional & scientific | 2005 |
| UKR SGF Ltd | Professional & scientific | 2019 |
| UKS Properties Limited | Real estate | 2019 |
| ULO Optics Limited | Manufacturing | 1982 |
| Ultimate Cars (Royston) Limited | Wholesale & retail | 2012 |
| Ultimate Sports Performance Limited | Arts & recreation | 2011 |
| ULTIMATE8 Fitness Hub Ltd | Arts & recreation | 2025 |
| Ultra Direct Limited | Information & communication | 2013 |
| Ultrasono Ltd | Health & social care | 2014 |
| Ultraviolet Designs Limited | Information & communication | 2023 |
| Umbra Lighting Ltd | Construction | 2018 |
| Undeliverable Limited | Extraterritorial | 2010 |
| Underground Electrical Services Limited | Construction | 2014 |
| Unearth Studio Ltd | Information & communication | 2019 |
| Unify Ventures Limited | Administrative & support | 2023 |
| Unique Collect Ltd | Wholesale & retail | 2022 |
| Unique Enhancement Ltd | Other services | 2018 |
| Unique FM Limited | Professional & scientific | 2024 |
| Unique Glam (UK) Ltd | Construction | 2023 |
| Unique Sourcing Point Ltd | Hospitality | 2020 |
| Uniqueness Limited | Administrative & support | 2003 |
| United Kables Ltd | Wholesale & retail | 2025 |
| United Kingdom Snacks Limited | Agriculture & fishing | 2017 |
| Unity Electrical Services Ltd | Construction | 2012 |
| Universal Cabling Solutions Ltd | Construction | 2023 |
| Universal Waste Management Limited | Water & waste | 2019 |
| Unlimited Potential and Possibilities Limited | Administrative & support | 2018 |
| Untitled Teaching Ltd | Education | 2025 |
| Upper Class Homes Ltd | Real estate | 2024 |
| Uppsilon Limited | Professional & scientific | 2020 |
| UPRISE22 Limited | Information & communication | 2022 |
| Upscapes Group Limited | Administrative & support | 2026 |
| Upscapes Limited | Other services | 2022 |
| Upthorpe Management Limited | Households | 2014 |
| Upwardbound Limited | Arts & recreation | 2022 |
| Urban Blueprint Ltd | Real estate | 2020 |
| Urban Lock-Up Rentals Ltd | Real estate | 2026 |
| Urban Plastics Limited | Wholesale & retail | 1987 |
| Urban Roots Hairdressing Ltd | Other services | 2024 |
| Urbanrock Properties Ltd | Real estate | 2025 |
| Urbanstyle Building Services Limited | Construction | 2012 |
| Urbanstyle Developments Ltd | Real estate | 2018 |
| Urgent Care Direct Ltd | Administrative & support | 2009 |
| Urvashi's Beauty Hub Ltd | Other services | 2026 |
| Usama Wain Limited | Health & social care | 2021 |
| Ustream Media Ltd | Professional & scientific | 2022 |
| Usvv Ltd | Professional & scientific | 2026 |
| Utkoma Ltd | Administrative & support | 2020 |
| Utopia Hair, Beauty & Aesthetics Ltd | Other services | 2025 |
| Utopia Holidays Limited | Administrative & support | 2009 |
| Utterly Lovely Productions Limited | Information & communication | 2008 |
| Uvichik Limited | Wholesale & retail | 2015 |
| Uzziel Enterprises Limited | Wholesale & retail | 2008 |
| V & P FOX Locksmiths Limited | Manufacturing | 2012 |
| V R Data Solutions Ltd | Information & communication | 2023 |
| V R Foods Ltd | Hospitality | 2023 |
| V R Mortgage Solutions Ltd | Financial services | 2016 |
| V Vision Solutions Ltd | Information & communication | 2018 |
| V4EVENTS Wedding Planner Limited | Information & communication | 2026 |
| VAH Group Ltd | Construction | 2024 |
| Vailas Visions Interiors Ltd | Real estate | 2025 |
| Valence Rigging Services Ltd | Information & communication | 2014 |
| Valentine Support Solutions Ltd | Other services | 2016 |
| Valley Joinery Limited | Construction | 1998 |
| Valley Way PUB Company Ltd | Hospitality | 2025 |
| Valorium Capital Ltd | Financial services | 2024 |
| Valthyr Ltd | Construction | 2023 |
| Valtur Services Ltd | Construction | 2016 |
| Van Raam UK Limited | Wholesale & retail | 2022 |
| Vanguard Hygiene Ltd | Administrative & support | 2025 |
| Vanisah Ltd | Construction | 2018 |
| Vanishing Point Creative Limited | Information & communication | 2012 |
| Vantage Landscaping Ltd | Administrative & support | 2026 |
| Varney Garden Services Ltd | Administrative & support | 2025 |
| Varospec UK Limited | Information & communication | 2012 |