| Ukplumbers Limited | Weymouth | 2023 |
| Ukreef Hampshire Ltd | Aldershot | 2025 |
| Ukreef Marine Limited | Teignmouth | 2024 |
| UL Fishing Co. Ltd | Inverness | 2025 |
| Ulcatra Forestry Limited | Carlisle | 2022 |
| Ulceby Farms Limited | Oakham | 1956 |
| Ullapool Charters Ltd | Ullapool | 2019 |
| Ullswater Limited | Penrith | 2025 |
| Ulster Dog Breeding Academy Ltd | Enniskillen | 2015 |
| Ulster Eggs Limited | | 1963 |
| Ulster Farm By-Products Limited | Dungannon | 1993 |
| Ulster Wool Group Limited | Co. Antrim | 1981 |
| Ultimate Fertilizers Limited | Chichester | 2011 |
| Ultimate K9 Ltd | Bedford | 2015 |
| Ultimate Network Solutions Limited | Brentwood | 2018 |
| Ultra Care Solutions Ltd | Ferryhill | 2025 |
| Ultra Tree Services Ltd | Benfleet | 2022 |
| Ultraponix Global CIC | Caerphilly | 2016 |
| Ului Limited | Stoke-On-Trent | 2025 |
| Ulvir Limited | Winchester | 1936 |
| Ulysses Research and Advisory Limited | Aylesbury | 2016 |
| Umaish Limited | London | 2023 |
| Umami Food and Farming Ltd | Plymouth | 2021 |
| Umbrian Eden (UK) Limited | London | 2022 |
| Umdlwane Ltd | Knutsford | 2021 |
| UME 24 Ltd | Craigavon | 2024 |
| UNA and Paul Boyle Limited | Bellanaleck | 2016 |
| Unam Limited | Banff | 2016 |
| Unania Ventures Limited | Welwyn Garden City | 2025 |
| Unbelievabullz Teesside Ltd | Stockton-On-Tees | 2020 |
| Uncle Salads Ltd | Hoddesdon | 2023 |
| Uncle Teds Limited | Halifax | 2019 |
| Uncletomschillis Ltd | Portsmouth | 2021 |
| Uncontrollabullz Limited | Birmingham | 2021 |
| Uncut Baits Limited | London | 2025 |
| Under Lyme Tree Care Ltd | Newcastle | 2016 |
| Under the Wire Limited | Sleaford | 2025 |
| Undercut Tree Services Limited | Pontefract | 2006 |
| Underground Trees Ltd | Edinburgh | 2021 |
| Underhill Farm Estates Limited | Betchworth | 2014 |
| Underhill Farm Ltd | Buxton | 2019 |
| Underhill Holdings Limited | Liverpool | 2019 |
| Underhill Limited | Stafford | 2022 |
| Underrock Transformation Ltd | London | 2018 |
| Understanding AG UK Limited | Kingston Upon Thames | 2025 |
| Underwood Contractors Ltd | Huntingdon | 2006 |
| Underwood Lodge Farm Ltd | Gaddesby | 2021 |
| Underwood Tree Surgeons Limited | Derbyshire | 2003 |
| Underwoodsman Limited | Tunbridge Wells | 2006 |
| UNI Management Solutions Ltd | Ruislip, | 2021 |
| Unicorn Grove Limited | Barking | 2025 |
| Unicorn Valley Farm Limited | Oxfordshire | 2024 |
| Unifreight Limited | Bristol | 2025 |
| Union Pest Control Ltd | Leamington Spa | 2026 |
| Union Trading Company Ltd | Chatham | 2023 |
| Unique Designs (Worcestershire) Limited | Worcester | 2012 |
| Unique Foods Limited | Long Bennington | 2007 |
| Unit Space Ltd | Liverpool | 2022 |
| United Agri Products Limited | Cheltenham | 1993 |
| United Clyde Angling Protective Association Limited | Wishaw | 1976 |
| United ESP Ltd | Northampton | 2022 |
| United Exports Ltd | Dorking | 2003 |
| United Fish Selling Limited | Buckie | 1982 |
| United Hotel Management Limited | London | 2016 |
| United Investment (Lincoln) Ltd | Brentwood | 2026 |
| United Kingdom Renderers' Association Limited | Newark | 2025 |
| United Kingdom Snacks Limited | Stevenage | 2017 |
| United Kingdom Woodland Assurance Standard (Ukwas) | Edinburgh | 1999 |
| United Oilseeds Marketing Limited | Devizes | 1979 |
| United PIG Co-Operative Ltd. | Wallingford | 1975 |
| United Potato Farmers Limited | York | 2009 |
| United Pulses Limited | Devizes | 2025 |
| Unity Fishing Company Limited | Fraserburgh | 1995 |
| Unity Fishing Services (Peterhead) Ltd | Peterhead | 2010 |
| Unity RP Ltd | Gott | 2025 |
| Unity Works Ltd | London | 2024 |
| Unium Bioscience Ltd | Doncaster | 2017 |
| Universal Aquaculture Limited | Burgess Hill | 2011 |
| Universal Horses Limited | Chester | 2016 |
| Universal Hydro Systems Ltd | Harrogate | 2014 |
| Universal Investment Capital Corporation UK Ltd | Bath | 2025 |
| Universal Product Supplies Ltd | Barnet | 2019 |
| Universal Stud Ltd | Newry | 2020 |
| Unleashed Indoor Dog Park Limited | Gourock | 2026 |
| Unleashed Paddocks Limited | Basingstoke | 2025 |
| Unlimited Mouse Ltd | Stoke On Trent | 2015 |
| Unlimited RAO Limited | Reigate | 2020 |
| Unlimited Success Ltd | Knaresborough | 2012 |
| Unst Shellfish Ltd. | Shetland | 2007 |
| Untainted Hearts Ltd | Kington | 2021 |
| Untamed Venison Limited | Sherborne | 2024 |
| Untapped Ventures Ltd | London | 2024 |
| Unthank Farming Ltd | Leyburn | 2023 |
| Unthank Farms Limited | London | 1998 |
| Unwin Estates Limited | Halstead | 1951 |
| Unyte Holdings Ltd | Market Harborough | 2025 |
| UP Cerne Limited | Up Cerne | 1979 |
| UP in Smoak Tree Services Ltd | Alexandria | 2025 |
| UP in the Ayers Tree Care Ltd | London | 2025 |
| UP Marden Farms Limited | Chichester | 2023 |