| Xpress Prints 24X7 Ltd | Manufacturing | 2024 |
| Xstruct Limited | Professional & scientific | 2019 |
| Xtranet Capital Limited | Construction | 2024 |
| XVM Limited | Information & communication | 2014 |
| Y02NAS Ltd | Real estate | 2025 |
| Yade Music Ltd | Arts & recreation | 2024 |
| Yandz & Co Ltd | Wholesale & retail | 2023 |
| Yasmin Maria Scardified Modeste Ltd | Extraterritorial | 2025 |
| YBN Services Limited | Other services | 2016 |
| Yellow FIN Productions Limited | Information & communication | 2017 |
| Yellow Tomato Homes Limited | Construction | 2019 |
| Yellow Tomato LLP | | 2006 |
| Yeohortho Limited | Health & social care | 2023 |
| YES2FITNESS Ltd | Other services | 2020 |
| Yetume Consulting Limited | Health & social care | 2021 |
| Yippee Productions Limited | Arts & recreation | 2005 |
| Yoda Limited | Real estate | 2021 |
| Yona Films Limited | Professional & scientific | 2013 |
| Yordle Limited | Households | 1990 |
| YOU I Limited | Information & communication | 2016 |
| YOU Want Pizza Ltd | Hospitality | 2025 |
| Youknowbest Ltd | Professional & scientific | 2016 |
| Young Capital Investments Limited | Other services | 2022 |
| Young Elite Academy Ltd | Education | 2025 |
| Young Trunk Designs Limited | Information & communication | 2015 |
| Youngeducation Ltd | Education | 2010 |
| Youngsdarealist Music Ltd | Information & communication | 2023 |
| Your Behavioural Economist Limited | Professional & scientific | 2016 |
| Your Behavioural Footprint Limited | Professional & scientific | 2016 |
| Your Future Ltd | Hospitality | 2017 |
| YPL UK Limited | Professional & scientific | 2021 |
| YSB Ltd | Construction | 2025 |
| YT Plumbing and Heating Limited | Construction | 2016 |
| YT Plumbing and Heating Services Limited | Construction | 2020 |
| YUSUF27 Ltd | Other services | 2026 |
| YVA Property Development Ltd | Real estate | 2021 |
| YZC Catering Invitation Limited | Hospitality | 2018 |
| Z & S Mohsini Limited | Real estate | 2022 |
| Z V S Consulting Limited | Education | 2025 |
| ZAF Construction Ltd | Professional & scientific | 2020 |
| Zakiya Dhansey Limited | Health & social care | 2016 |
| Zanzar Consultancy Ltd | Administrative & support | 2010 |
| Zara UK Holdco Limited | Financial services | 2017 |
| Zara UK Topco Limited | Wholesale & retail | 2015 |
| Zaroga Traders Ltd | Wholesale & retail | 2023 |
| Zaskin College Limited | Education | 2002 |
| Zaverocore Solutions Ltd | Information & communication | 2026 |
| Zawa Limited | Health & social care | 2015 |
| Zcsu Limited | Professional & scientific | 2022 |
| ZE Quantity Surveying & Commercial Consultancy Ltd | Professional & scientific | 2026 |
| Zebra Development Limited | Construction | 2016 |
| Zecolive Company Limited | Health & social care | 2020 |
| Zedlocum Ltd | Health & social care | 2022 |
| Zeemhur Pacific Limited | Real estate | 2022 |
| Zeka Tech Limited | Wholesale & retail | 2021 |
| Zela Solutions Limited | Construction | 2016 |
| ZEN Hair and Beauty Stevenage Ltd | Other services | 2024 |
| Zero Deposit Limited | Real estate | 2019 |
| Zeytra Ltd | Wholesale & retail | 2025 |
| Zhou Orthopaedics Ltd | Health & social care | 2025 |
| Zimboid Limited | Health & social care | 2015 |
| Zimmer Limited | Other services | 2019 |
| Zinger Munch Limited | Hospitality | 2019 |
| Zippy ZEN Ltd | Information & communication | 2023 |
| Ziva Group Ltd | Information & communication | 2017 |
| Zivi Limited | Professional & scientific | 2009 |
| ZMC Global Ltd | Wholesale & retail | 2019 |
| ZOE Grey Ltd | Professional & scientific | 2024 |
| ZOE Lewis Digital Limited | Professional & scientific | 2013 |
| ZR Enterprise Jhenaidah Limited | Hospitality | 2019 |
| Zuffys Ltd | Wholesale & retail | 2019 |
| Zuriel Ventures Limited | Health & social care | 2014 |
| ZXM Management Ltd | Information & communication | 2025 |
| Zxnqah Ltd | Construction | 2024 |