| WRD Electrical Ltd | Construction | 2022 |
| Wrench and Word Motorcycle Centre Limited | Wholesale & retail | 2026 |
| Wrens Investments Limited | Real estate | 2010 |
| Writers Reign Limited | Professional & scientific | 2013 |
| WRL Trading Limited | Manufacturing | 2015 |
| WWK 1 Limited | Financial services | 2014 |
| WWK 2 Limited | Professional & scientific | 2016 |
| Wyatt Mews (Witney) Management Company Limited | Households | 2021 |
| Wycrest Limited | Administrative & support | 1996 |
| WYE Residential (Stokenchurch) LLP | | 2020 |
| WYE Residential LLP | | 2009 |
| Wyre Repairs Limited | Manufacturing | 1985 |
| X-Treme Clean Facilities Management Limited | Administrative & support | 2019 |
| XAM Services Limited | Information & communication | 2018 |
| Xander Hauleage Ltd | Transport & logistics | 2017 |
| Xchell Limited | Wholesale & retail | 2021 |
| Xcorso Limited | Professional & scientific | 2022 |
| Xelibri Ltd | Professional & scientific | 2016 |
| Xenon Management Training & Recruitment Limited | Professional & scientific | 2002 |
| XER Payroll Services Ltd | Information & communication | 2024 |
| Xoipsys LLP | | 2005 |
| Xperience Marketing Solutions Limited | Professional & scientific | 2013 |
| Xploratix Holding Ltd | Information & communication | 2020 |
| Xtreme Accounting Limited | Professional & scientific | 2014 |
| Xyenterprise Limited | Information & communication | 1983 |
| Xylem Creative Services Ltd | Professional & scientific | 2025 |
| Y Bryn Wind Farm Limited | Energy | 2019 |
| Y.& L.Jacobs(Windsor)Limited | Real estate | 1960 |
| Yadra LLP | | 2026 |
| Yang-Tobutt Holdings Ltd | Real estate | 2026 |
| Yapi Limited | Wholesale & retail | 2014 |
| Yapi West Ltd | Real estate | 2025 |
| Yashtech Ltd | Information & communication | 2009 |
| Yasir Electronics Limited | Wholesale & retail | 2024 |
| YAV Enterprises Ltd | Transport & logistics | 2023 |
| YE Olde Farm Shop Ltd | Wholesale & retail | 2025 |
| Yedon Limited | Health & social care | 2019 |
| Yellow Mustard Design Limited | Professional & scientific | 2007 |
| Yeovil Crane Hire Ltd | Transport & logistics | 2025 |
| YES Events Ltd. | Administrative & support | 2002 |
| YEW Accountancy Limited | Professional & scientific | 2015 |
| YG Gynaecology Limited | Health & social care | 2017 |
| Yimu Education Ltd | Professional & scientific | 2021 |
| YM Bridge Ltd | Real estate | 2020 |
| YM Fruits Limited | Wholesale & retail | 2023 |
| Yolo Creations Ltd | Wholesale & retail | 2023 |
| Yorkshire Data Centres Limited | Extraterritorial | 2008 |
| YOU IT Limited | Information & communication | 2010 |
| YOU Present Limited | Information & communication | 2009 |
| YOU, ME & Myself Ltd | Information & communication | 2026 |
| Your Oasiss Ltd | Other services | 2026 |
| Your Smile Turkey Ltd | Administrative & support | 2023 |
| Your Words Your World CIC | Arts & recreation | 2025 |
| Yourgridpilot Ltd | Information & communication | 2026 |
| Yourz to EAT Catering and Baguette Bar Ltd | Hospitality | 2025 |
| Youthful Revival Ltd | Other services | 2024 |
| Ytron-Quadro (UK) Limited | Wholesale & retail | 1984 |
| Yugen Healing Ltd | Wholesale & retail | 2025 |
| Yukon 1000 Ltd | Arts & recreation | 2017 |
| Z & C Perrott Properties Ltd | Real estate | 2023 |
| Z Khan Investments Ltd | Real estate | 2022 |
| Z-Lister Ltd | Information & communication | 2025 |
| Zaadib Limited | Information & communication | 2014 |
| Zaal G Limited | Wholesale & retail | 2024 |
| Zada-Technology Ltd. | Administrative & support | 2000 |
| Zanshin Markets Ltd | Arts & recreation | 2013 |
| Zass Calculated Infrastructure Ltd | Professional & scientific | 2019 |
| Zaydaad Limited | Real estate | 2022 |
| Zbees Ltd | Information & communication | 2023 |
| Zebra Accounting (Thames Valley) Limited | Professional & scientific | 2005 |
| Zebra Accounting Limited | Extraterritorial | 2007 |
| Zeek Trading Ltd | Wholesale & retail | 2024 |
| Zeekia Home Ltd | Wholesale & retail | 2025 |
| Zein Chaudhry Limited | Manufacturing | 2019 |
| Zemer SK Ltd | Construction | 2020 |
| ZEN Wellbeing Ltd. | Other services | 2013 |
| Zena Zuberi Designs Limited | Professional & scientific | 2015 |
| Zenith Canopy Structures Limited | Construction | 2004 |
| Zenith Exhibitions and Marquees Limited | Administrative & support | 2025 |
| Zenith Racing Club Ltd | Arts & recreation | 2021 |
| Zenith Racing Ltd | Agriculture & fishing | 2019 |
| Zenmedix Limited | Information & communication | 2025 |
| Zens Property Ltd | Real estate | 2024 |
| Zephyrairsolutions Ltd | Construction | 2025 |
| Zero Nine Consulting Limited | Information & communication | 2006 |
| Zero Nine Services Ltd | Administrative & support | 2025 |
| Zeteon Limited | Wholesale & retail | 2009 |
| Zetland Court Residents Association Limited | Hospitality | 1963 |
| ZH Paramount Services Ltd | Administrative & support | 2013 |
| Zhan Cheng Ltd | Hospitality | 2018 |
| ZHR Ltd | Administrative & support | 2014 |
| Zilver Actro Properties Limited | Real estate | 2024 |
| ZIM Group Limited | Administrative & support | 2025 |
| Zingase Limited | Real estate | 2019 |
| ZML Services Ltd | Transport & logistics | 2025 |
| Zokyo Ltd | Information & communication | 2016 |
| Zoological Society of the Isle of Wight Ltd | Arts & recreation | 2026 |
| Zoom Autos Ltd | Transport & logistics | 2022 |
| Zoomera Ltd | Wholesale & retail | 2025 |
| Zoomlion Construction and Agriculture UK Limited | Wholesale & retail | 2025 |