| World Superstars Limited | Administrative & support | 1997 |
| Worthwhile Recruitment Ltd | Administrative & support | 2024 |
| WP Installz Ltd | Wholesale & retail | 2026 |
| Wrblo Community Interest Company | Administrative & support | 2017 |
| Wright Futures Support Ltd | Health & social care | 2020 |
| Wright Tiles Ltd | Wholesale & retail | 2003 |
| Wrkshp Ltd | Professional & scientific | 2024 |
| WT Logistics Ltd | Transport & logistics | 2022 |
| WTM Solutions Limited | Administrative & support | 2023 |
| WTS Investing Limited | Financial services | 2023 |
| Www.Jmbmotorsport.Com Ltd | Wholesale & retail | 2017 |
| Www.Ridestalbans.Com Ltd | Wholesale & retail | 2020 |
| Wyckoff Properties Limited | Real estate | 2012 |
| Wynnebrook Ltd | Financial services | 2026 |
| XB3 Dance Productions Ltd | Information & communication | 2025 |
| Xeat.Co.Uk PVT Ltd | Hospitality | 2020 |
| XFW Limited | Information & communication | 2026 |
| Xintara Ltd | Other services | 2018 |
| Xiro IT Solutions PVT Ltd | Information & communication | 2021 |
| XJ Property Investment Limited | Real estate | 2017 |
| Xlent ERP Consulting Limited | Information & communication | 2011 |
| XON Services Limited | Construction | 2021 |
| XTG Consulting Limited | Professional & scientific | 2024 |
| Yaseeb Ltd | Professional & scientific | 2021 |
| YCT Technical Services Ltd | Other services | 2023 |
| Yeatei Ltd | Hospitality | 2025 |
| Yeldia Ltd | Information & communication | 2013 |
| Yewstock Limited | Real estate | 1960 |
| YKM Solutions Ltd | Information & communication | 2019 |
| Yohrs Ltd | Administrative & support | 2021 |
| Yoka Boxing Limited | Arts & recreation | 2024 |
| Yoohoo Build Ltd | Construction | 2010 |
| Youngship London Limited | Health & social care | 2025 |
| Your Local Media Limited | Information & communication | 2011 |
| Youth With a Mission Harpenden | Other services | 2013 |
| Youth With a Mission Limited | Other services | 1972 |
| YY Builder Limited | Administrative & support | 2025 |
| ZAR Financial Consulting Services Limited | Financial services | 2012 |
| Zaraka Consultancy Ltd | Professional & scientific | 2023 |
| Zashir Ltd | Health & social care | 2024 |
| ZAZAMED21 Ltd | Health & social care | 2020 |
| ZB Consulting Services Ltd | Professional & scientific | 2024 |
| Zebra Stripe Films Limited | Information & communication | 2012 |
| Zebra Technical Recruitment Ltd | Administrative & support | 2009 |
| Zemal and Haniya Ltd | Wholesale & retail | 2025 |
| Zemaye Consult Limited | Professional & scientific | 2001 |
| Zendo PEN Ltd | Information & communication | 2017 |
| Zenga Data Limited | Wholesale & retail | 2019 |
| Zing Wellness Ltd | Other services | 2022 |
| Zios Pizzeria Ltd | Hospitality | 2023 |
| Zippy Enterrprises Limited | Real estate | 2020 |
| ZOE Weightman Ltd | Professional & scientific | 2018 |
| Zooatronic Productions CIC | Professional & scientific | 2024 |