| Xenergie Limited | Professional & scientific | 2018 |
| Xenia Housing Ltd | Public administration | 2022 |
| Xeno GP Ltd | Professional & scientific | 2021 |
| Xenon Star Ltd | Information & communication | 2015 |
| Xiangyu International UK Ltd | Wholesale & retail | 2025 |
| XO Dough Ltd | Manufacturing | 2020 |
| Xohto Limited | Wholesale & retail | 2025 |
| XRP Group Limited | Wholesale & retail | 2021 |
| Xtpc Holdings Ltd | Manufacturing | 2018 |
| Xtrahosting Limited | Information & communication | 2025 |
| Xtreme Design Ltd | Professional & scientific | 1998 |
| Xtreme Team Ltd | Arts & recreation | 2017 |
| Xvir Healthcare Limited | Financial services | 2016 |
| XY Management Solutions Ltd | Construction | 2014 |
| Xybit Limited | Wholesale & retail | 2026 |
| Xylem Systems Ltd | Professional & scientific | 2026 |
| Xylo Two Ltd | Professional & scientific | 2019 |
| Xynstak Limited | Professional & scientific | 2024 |
| Xyntra Limited | Manufacturing | 2013 |
| Y Pellets Limited | Manufacturing | 2016 |
| Y&A Enterprises Ltd | Wholesale & retail | 2024 |
| Y&R Estates Ltd | Households | 2026 |
| Y.D. Enterprise Ltd | Professional & scientific | 2009 |
| Yahchayil Limited | Information & communication | 2023 |
| Yamas Events Ltd | Hospitality | 2021 |
| Yangs Holding Limited | Professional & scientific | 2022 |
| YAP & SON Limited | Real estate | 2021 |
| Yapstar Limited | Hospitality | 2019 |
| Yarn Communications Ltd | Professional & scientific | 2023 |
| Yarwood Memorial Products Ltd | Other services | 2017 |
| Yatesbury Garth Fish Bar Limited | Hospitality | 2020 |
| Yatzen Limited | Hospitality | 2022 |
| Yemad Solutions UK Limited | Health & social care | 2015 |
| YEN Financial Limited | Financial services | 2015 |
| Yenge Consultancy Limited | Professional & scientific | 2018 |
| YEP Schools Direct Limited | Professional & scientific | 2014 |
| Yeske Ltd | Wholesale & retail | 2025 |
| Yessicake Limited | Hospitality | 2026 |
| Yeta Trades Limited | Financial services | 2024 |
| YEW Gate Limited | Households | 2021 |
| YH Education Consultancy Ltd | Education | 2012 |
| Yinka Folawiyo & Sons (London) Limited | Other services | 1975 |
| Ymca Essex | Health & social care | 1996 |
| Ymca Essex (Trading) Ltd. | Other services | 1995 |
| Ymjk Ltd | Health & social care | 2020 |
| Yogini Wellness Ltd | Other services | 2023 |
| Yoko Limited | Administrative & support | 2026 |
| YOU Before ME Care Limited | Health & social care | 2017 |
| YOU First Home Improvements Ltd | Construction | 2025 |
| YOU Talk Insurance Limited | Information & communication | 2011 |
| You'Re Caked Ltd | Hospitality | 2022 |
| Youngs Recruitment Limited | Other services | 2020 |
| Youngvale Limited | Construction | 2016 |
| Your Claim Limited | Other services | 2016 |
| Your Leadership Footprint Limited | Administrative & support | 2010 |
| Your New Mind Ltd | Education | 2024 |
| Your Sustainable Match Limited | Information & communication | 2025 |
| Your Unlimited Potential Limited | Professional & scientific | 2015 |
| Yourlocalshopco Ltd | Wholesale & retail | 2020 |
| Yousuf Data Soft Limited | Information & communication | 2023 |
| Youty Business Solutions Ltd | Energy | 2024 |
| Ypcare Ltd | Health & social care | 2015 |
| Ypharm Ltd | Administrative & support | 2015 |
| Yuki Nest Ltd | Real estate | 2026 |
| Yvonne Thackray Healthcare Advisory Ltd | Professional & scientific | 2026 |
| Z.L.F Investments Limited | Real estate | 2025 |
| ZA ZA OPS Limited | Hospitality | 2014 |
| ZAC Oliver Limited | Arts & recreation | 2025 |
| Zadir Trading Limited | Wholesale & retail | 2026 |
| Zaero Design UK Ltd | Wholesale & retail | 2024 |
| Zahaa Medics Limited | Health & social care | 2021 |
| Zaktah Ltd | Wholesale & retail | 2019 |
| Zamyn Technologies Ltd | Information & communication | 2025 |
| Zanco Models Limited | Manufacturing | 2015 |
| Zandel Ltd | Professional & scientific | 2016 |
| ZAP Ventures Limited | Real estate | 2024 |
| Zara Muse Holdings Ltd | Financial services | 2025 |
| Zara Muse Limited | Arts & recreation | 2025 |
| Zarchem Limited | Manufacturing | 2021 |
| Zare Essex Ltd | Health & social care | 2025 |
| Zarijay Limited | Health & social care | 2025 |
| Zarterone Services Limited | Construction | 2003 |
| Zealous Services Limited | Real estate | 2025 |
| Zebra Games Ltd | Information & communication | 2025 |
| Zebra Homes Limited | Professional & scientific | 2010 |
| Zedalise Limited | Administrative & support | 2019 |
| Zeedoc Ltd | Health & social care | 2024 |
| Zeg.Ai Ltd | Information & communication | 2018 |
| ZEN Digital Publishing Limited | Information & communication | 2018 |
| ZEN Living Properties Limited | Real estate | 2018 |
| Zenospace International Limited | Professional & scientific | 2015 |
| Zenotalent Ltd | Information & communication | 2026 |
| Zenta Commerce Ltd | Wholesale & retail | 2025 |
| Zenyk Ltd | Construction | 2026 |
| Zephyr DU Barry Limited | Financial services | 2019 |
| Zero Management Services Ltd | Administrative & support | 2023 |
| Zero One Networking Ltd | Information & communication | 2017 |
| Zero Pepper Ltd | Professional & scientific | 2024 |
| Zethzidane Properties Limited | Real estate | 2020 |
| Zeus Luxury Limited | Wholesale & retail | 2020 |