| UK Roadworks Group Ltd | Construction | 2025 |
| UK Seaman Ltd. | Hospitality | 2019 |
| UK Stem Limited | Professional & scientific | 2015 |
| UK Study Abroad by Pitcha Limited | Education | 2025 |
| UK Trading Experts Ltd | Wholesale & retail | 2025 |
| UK Whisky Society Ltd | Education | 2023 |
| UK Yacht Charters Limited | Administrative & support | 2023 |
| Uknight Solutions Ltd | Administrative & support | 2015 |
| Ukommerce Ltd | Wholesale & retail | 2026 |
| Ukozin Services Limited | Professional & scientific | 2016 |
| Ukyc Limited | Wholesale & retail | 2024 |
| Ultimate Sports Dive Co Limited | Information & communication | 2006 |
| Ultimate Sports Media Limited | Information & communication | 2005 |
| Ultra Fire & Security Ltd | Administrative & support | 2020 |
| Ultra Seal Flat Roofing Limited | Construction | 2013 |
| Ultrack Limited | Hospitality | 2025 |
| Umbrella Insight Ltd | Professional & scientific | 2016 |
| Unconventional Design Limited | Construction | 2017 |
| Under the Influence [Yorkshire] Ltd | Real estate | 2013 |
| Under the Stairs Digital Limited | Other services | 2014 |
| Under the Stairs Properties Ltd | Real estate | 2025 |
| Undershaft (Nulla) Limited | Extraterritorial | 1919 |
| Undershaft FAL Limited | Financial services | 2007 |
| Undershaft Fplla Limited | Extraterritorial | 1982 |
| Undershaft Slpm Limited | Extraterritorial | 1973 |
| Undershot Ltd | Professional & scientific | 2000 |
| Underwood Consultants Limited | Professional & scientific | 2024 |
| Unfiltered Health Space CIC | Health & social care | 2026 |
| Unguenta Paradisi Ltd | Manufacturing | 2025 |
| Unicorn Pegasus Ltd | Professional & scientific | 2011 |
| Unicorns Travel Tourism Limited | Administrative & support | 2026 |
| Uniglad Ingredients UK Limited | Wholesale & retail | 2014 |
| Uniliving Limited | Extraterritorial | 2016 |
| Union EPS Ltd | Transport & logistics | 2018 |
| Unique Barber York Ltd | Other services | 2025 |
| Unique Hair and Beauty (Bello) Ltd | Other services | 2016 |
| Unique Management Services LLP | | 2024 |
| Unique Minds Limited | Extraterritorial | 2023 |
| Unique York Limited | Other services | 2017 |
| Unirend Limited | Manufacturing | 2020 |
| Unit 17 Limited | Extraterritorial | 2021 |
| Unit 2 Management Limited | Water & waste | 2004 |
| Unit Seventeen Limited | Extraterritorial | 2021 |
| United Colours of Business Limited | Professional & scientific | 2014 |
| United Construction Projects Ltd | Administrative & support | 2023 |
| United Kingdom Drones Ltd | Information & communication | 2017 |
| United Potato Farmers Limited | Agriculture & fishing | 2009 |
| United Road Services Ltd | Construction | 2025 |
| Uniti Software Limited | Extraterritorial | 2021 |
| Unity Health Trading Limited | Health & social care | 2013 |
| Unity Practice Solutions Ltd | Professional & scientific | 2024 |
| Univercity Consulting Limited | Professional & scientific | 2020 |
| Universal Electrics (York) Ltd. | Manufacturing | 2013 |
| University of York International Pathway College LLP | | 2015 |
| University of York Music Press | Information & communication | 1997 |
| University of York Pension Trust Limited (the) | Financial services | 1964 |
| University of York Students' Union | Education | 2017 |
| Unlimited Entertainment Limited | Information & communication | 2018 |
| Unovik Ltd | Wholesale & retail | 2025 |
| Untagged Limited | Real estate | 2011 |
| Untanas Semveta Limited | Real estate | 2024 |
| Untethered Ltd | Professional & scientific | 2022 |
| Unveiling Curtains Limited | Other services | 2017 |
| UP Consultancy Ltd | Professional & scientific | 2025 |
| UP North Trading Ltd | Manufacturing | 2021 |
| Upec Matches Ltd | Manufacturing | 2024 |
| Upfront Cafe Ltd | Hospitality | 2025 |
| Uplands Way Vets Limited | Extraterritorial | 2006 |
| Upngo Ltd | Information & communication | 2024 |
| Upper 10 Limited | Wholesale & retail | 2004 |
| Upper Case Wines Limited | Wholesale & retail | 2009 |
| Upper Norby Limited | Professional & scientific | 2025 |
| Upsidedowndesign Limited | Arts & recreation | 2012 |
| Upson Ventures Ltd | Administrative & support | 2016 |
| Upton Controls Ltd | Construction | 2018 |
| Urban Autos York Ltd | Wholesale & retail | 2025 |
| Urban Chondros Ltd | Agriculture & fishing | 2023 |
| Urban Constrictors Ltd | Agriculture & fishing | 2017 |
| Urban Cozy Properties Ltd | Real estate | 2021 |
| Urban Cube Lettings Ltd | Real estate | 2023 |
| Urban Developments (York) Limited | Construction | 2020 |
| Urban Dream Properties Ltd | Households | 2024 |
| Urban Hair (Boroughbridge) Limited | Other services | 2013 |
| Urban House Ventures Ltd | Real estate | 2024 |
| Urban Lifestyle Limited | Hospitality | 2013 |
| Urban Media Publishing Ltd | Information & communication | 2006 |
| Urban Properties York LLP | | 2019 |
| Urban Software Ltd | Information & communication | 2019 |
| Urban Space Potential Limited | Construction | 2017 |
| Urban Stitch Ltd | Manufacturing | 2021 |
| Urban Tales Production Ltd | Information & communication | 2025 |
| Urban Village Hotels Ltd | Professional & scientific | 2010 |
| Urbis Design Limited | Manufacturing | 2005 |
| Urchin Limited | Manufacturing | 1997 |
| Ursa Engineering Solutions Ltd | Professional & scientific | 2018 |
| Ursus Services Limited | Professional & scientific | 2015 |
| Uscale Marketing Ltd | Professional & scientific | 2022 |
| Usercoded Ltd | Information & communication | 2025 |
| Usworth Hall Management NO.1 Limited | Real estate | 2007 |
| Utilities Metering Ltd | Information & communication | 2026 |