| Wymark Limited | Manufacturing | 1979 |
| Wynner Investment Limited | Financial services | 2021 |
| Wysis Partnership Limited | Professional & scientific | 2018 |
| Wyspa Ltd | Wholesale & retail | 2020 |
| Wyvern Garage Car Sales Ltd | Wholesale & retail | 2025 |
| Wyvern Grove Management Limited | Households | 1988 |
| X-Cell Assets Limited | Administrative & support | 2025 |
| X-Cell Holdings Limited | Financial services | 2023 |
| X-Cell Telecom Limited | Information & communication | 2023 |
| X-Net Consulting Ltd | Professional & scientific | 2025 |
| X-Sb Solutions Limited | Professional & scientific | 2025 |
| X3V Engineering Consultancy Limited | Professional & scientific | 2025 |
| Xabrio Limited | Information & communication | 2012 |
| Xait Ltd | Information & communication | 1999 |
| Xanagrams Ltd | Information & communication | 2019 |
| XC Associates Ltd | Professional & scientific | 2010 |
| Xecutivetalent Limited | Administrative & support | 2017 |
| Xenex Disinfection Services Limited | Administrative & support | 2013 |
| Xero Training Centre Limited | Education | 2015 |
| XIN Ying Takeaway Ltd | Hospitality | 2012 |
| Xinyueke Industry & Trade UK Ltd | Wholesale & retail | 2024 |
| Xiva Ltd | Financial services | 2023 |
| Xkaisen Ltd. | Real estate | 2017 |
| Xlsm Ltd | Professional & scientific | 2025 |
| XO Holdings Limited | Financial services | 2018 |
| XP Brands Ltd | Manufacturing | 2021 |
| Xprv Limited | Information & communication | 2023 |
| Xter Ltd | Transport & logistics | 2014 |
| Xtreme Property Sourcing Ltd | Real estate | 2026 |
| Xuan RUI Ltd | Hospitality | 2017 |
| Xylomed Pharmaceuticals Limited | Manufacturing | 2016 |
| Y&Y Docklands Ltd | Construction | 2011 |
| Y-Fets Ltd | Professional & scientific | 2026 |
| Y2 Investments Limited | Real estate | 2026 |
| Yablu Limited | Information & communication | 2011 |
| Yafrica Travel Limited | Administrative & support | 2024 |
| Yagmur INK Limited | Arts & recreation | 2026 |
| Yakiniku Restaurants UK Ltd | Hospitality | 2025 |
| Yalta European Strategy Limited | Administrative & support | 2006 |
| Yama Sushi Ltd | Hospitality | 2021 |
| Yang T Ze(Uk) Ltd | Hospitality | 2026 |
| Yapp Associates Limited | Construction | 2009 |
| Yards Farm Ecoenergy Limited | Energy | 2013 |
| Yarn Elegance Ltd | Wholesale & retail | 2025 |
| Yaro Construction Ltd | Construction | 2023 |
| Yaya Tech Ltd | Professional & scientific | 2023 |
| Yeates Investments Limited | Real estate | 2025 |
| Yeldham Court Management Limited | Households | 2002 |
| Yellohammer Consulting Ltd | Professional & scientific | 2022 |
| Yellow Beetroot Ltd | Professional & scientific | 2014 |
| Yellow Kite Design Studio Limited | Professional & scientific | 2023 |
| Yellow Shark Productions Ltd | Arts & recreation | 2015 |
| Yellow Shark Studios LLP | | 2022 |
| Yellowrattle Coaching Ltd | Professional & scientific | 2021 |
| Yero Holdings Limited | Financial services | 2026 |
| YES Chef Creative Ltd | Manufacturing | 2026 |
| YES Guardians Limited | Education | 2020 |
| Yetter Limited | Health & social care | 2025 |
| Yewtree.Com Limited | Real estate | 2008 |
| Yilmaz Electric Ltd | Construction | 2019 |
| Yipikiyay Ltd | Information & communication | 2018 |
| Yiproco Limited | Real estate | 2017 |
| Ymkw Ltd | Hospitality | 2025 |
| Ynys Investments Ltd | Real estate | 2024 |
| YO Home Limited | Real estate | 2020 |
| Yoga IS My Superpower Ltd | Wholesale & retail | 2020 |
| Yoga Therapy Association | Other services | 2022 |
| Yogawing Limited | Households | 1979 |
| Yogo Experience Ltd | Wholesale & retail | 2022 |
| Yoodooapp Ltd | Professional & scientific | 2022 |
| York & Lazenby Property Limited | Real estate | 2021 |
| York Family Books Ltd | Wholesale & retail | 2019 |
| York House Centre Limited | Health & social care | 2014 |
| York Terrace, Cheltenham, (Management Company) Limited | Households | 1979 |
| Yorke Property Ltd | Real estate | 2012 |
| Yorkshire Burrito Limited | Hospitality | 2016 |
| YOS Tiling Services Ltd | Construction | 2025 |
| Yoshie Productions Ltd | Professional & scientific | 2026 |
| YOU Need a Budget UK Ltd | Information & communication | 2021 |
| Yougoow Digital Ltd | Information & communication | 2025 |
| Youknowwho Property Limited | Real estate | 2005 |
| Youllplan Ltd | Professional & scientific | 2010 |
| Young & Gilling Ltd | Real estate | 2000 |
| Young & Gilling Residential Ltd | Extraterritorial | 2004 |
| Youngsons Gloucester Ltd | Construction | 2009 |
| Youpay Limited | Information & communication | 2026 |
| Your Computer Assistant Ltd | Information & communication | 2018 |
| Your Independent Broker F.S Ltd | Financial services | 2025 |
| Your Inspired Living Ltd | Real estate | 2021 |
| Your Perfect Recipes Ltd | Information & communication | 2025 |
| Your Store Limited | Professional & scientific | 1995 |
| Your Village Ltd | Administrative & support | 2026 |
| Your Voice Marketing Ltd | Professional & scientific | 2023 |
| Yourlocalparts Limited | Wholesale & retail | 2025 |
| Youtart Ltd | Wholesale & retail | 2026 |
| Yoyo Info UK Ltd | Wholesale & retail | 2012 |
| YPB Ltd | Financial services | 2025 |
| Ystwyth Veterinary Practice Ltd | Professional & scientific | 2008 |
| Yvop Ltd | Information & communication | 2022 |
| YY Tech Ltd | Information & communication | 2023 |