| X-Pio Ltd | Professional & scientific | 2020 |
| Xanadu Advisory Limited | Administrative & support | 2020 |
| Xander's Bar Limited | Hospitality | 2022 |
| Xenios Consulting Limited | Professional & scientific | 2001 |
| Xera Homes Limited | Construction | 2022 |
| Xera Innovations Limited | Information & communication | 2021 |
| XL Brew Ltd | Manufacturing | 2013 |
| Xsav Ltd | Arts & recreation | 2018 |
| Yeah US! Limited | Information & communication | 2012 |
| Yellapro Limited | Wholesale & retail | 2016 |
| Yellow Brick Road Property Limited | Real estate | 2018 |
| YEW Tree Close Management Company Limited | Households | 2008 |
| YEW Tree Contractors Limited | Administrative & support | 2004 |
| YEW Tree Court Kingston Bagpuize Limited | Households | 2021 |
| YEW Tree Mews (Management) Limited | Households | 1997 |
| Yfwih Your First Wealth IS Health Ltd | Hospitality | 2019 |
| Yoga Leigh Wellbeing Limited | Health & social care | 2026 |
| Young Engineering Supplies Limited | Wholesale & retail | 2006 |
| Youngson Plastering Limited | Construction | 2018 |
| Your Barbers (Witney) LLP | | 2019 |
| Youtrition Ltd | Health & social care | 2025 |
| Zabmedia Ltd | Real estate | 2014 |
| Zadok Media Limited | Arts & recreation | 2012 |
| Zainul Leitch Consulting Limited | Professional & scientific | 2005 |
| Zandato Limited | Professional & scientific | 2012 |
| Zenga Oxford Limited | Extraterritorial | 2020 |
| Zenrise Solutions Limited | Real estate | 2024 |
| Zero Electrical Limited | Manufacturing | 2021 |
| Zero.Four Agency Ltd | Other services | 2025 |
| Zeroori Innovations Ltd | Wholesale & retail | 2023 |
| Zetica Limited | Professional & scientific | 2000 |
| Zetica Rail Limited | Professional & scientific | 2000 |
| Zetta Connect Limited | Information & communication | 2017 |
| Zetta Holdings Ltd | Information & communication | 2025 |
| Zinco Green Roof Systems Limited | Construction | 2012 |
| Zircotec Holdings Limited | Professional & scientific | 2013 |
| Zircotec IP Limited | Professional & scientific | 2013 |
| Zircotec Limited | Manufacturing | 2008 |
| Znaheart Ltd | Professional & scientific | 2023 |
| Zofam Limited | Health & social care | 2016 |