| Xerox Trading Enterprises Limited | Extraterritorial | 1984 |
| Xerox UK Holdings Limited | Financial services | 1998 |
| Xescapes Limited | Administrative & support | 2024 |
| XIT Solutions Ltd | Information & communication | 2000 |
| Xitin Managed Services Limited | Real estate | 2012 |
| Xlnsys Ltd | Information & communication | 2008 |
| Xochitl Husbands Properties Ltd | Real estate | 2026 |
| XP Logistics Ltd | Transport & logistics | 2018 |
| Xpedite Solutions Ltd | Professional & scientific | 2016 |
| Xportxcel Ltd | Wholesale & retail | 2025 |
| Xpress ALL Limited | Other services | 2022 |
| Xpress Grill (Uxbridge) Ltd | Hospitality | 2025 |
| Xpwconsulting Limited | Professional & scientific | 2013 |
| XRI Limited | Extraterritorial | 1947 |
| XRO Limited | Extraterritorial | 1937 |
| Xvii Management Ltd | Households | 2025 |
| XX Development Ltd | Construction | 2026 |
| XX Property Limited | Construction | 2024 |
| Xyza Ltd | Wholesale & retail | 2025 |
| Y JAK Developments Ltd | Construction | 2021 |
| Y.O.P ENG Limited | Administrative & support | 2020 |
| Yateley Financial Services Ltd | Financial services | 2023 |
| Yellow Brick Road Limited | Information & communication | 1986 |
| YH Management Ltd | Information & communication | 2021 |
| YHN Ltd | Wholesale & retail | 2024 |
| YLF Homes Ltd | Construction | 2022 |
| YLF Ltd | Professional & scientific | 2018 |
| YLJ Limited | Administrative & support | 2024 |
| YMA Energy Deals Ltd | Other services | 2025 |
| Yoga.Ed Ltd | Education | 2019 |
| Yogamaya Limited | Information & communication | 1998 |
| Yohannes Property Group Ltd | Real estate | 2022 |
| Yondry Ltd | Administrative & support | 2026 |
| Yoplait UK Limited | Wholesale & retail | 1991 |
| Yorkshire Meat Exports Ltd | Wholesale & retail | 2019 |
| Yorkshire Rose Properties Ltd | Real estate | 2017 |
| YOU Dream WE Build Ltd | Construction | 2016 |
| Youcan Consulting Ltd. | Information & communication | 2010 |
| Young Millions Limited | Administrative & support | 2011 |
| Younique Gifts Limited | Wholesale & retail | 2021 |
| Your Best Buy Limited | Wholesale & retail | 2026 |
| Your Canal Boat C.I.C. | Education | 2020 |
| Your Glassroom Ltd | Professional & scientific | 2025 |
| Your Luxury Key Ltd | Transport & logistics | 2025 |
| Your Stationery Limited | Wholesale & retail | 1989 |
| Yourtrolley Ltd | Wholesale & retail | 2021 |
| Yousaf Mian Consulting Ltd | Professional & scientific | 2016 |
| YPL Fashion Ltd | Wholesale & retail | 2023 |
| YUM Crust Pizza Ltd | Hospitality | 2026 |
| Yumchi London Ltd | Hospitality | 2026 |
| Yumchi Uxbridge Ltd | Hospitality | 2018 |
| Yummy OBB Ltd | Hospitality | 2022 |
| YW Design Ltd | Professional & scientific | 2024 |
| YXZ Limited | Households | 2021 |
| Yyagi Ltd | Information & communication | 2022 |
| Z & B Property London Ltd | Real estate | 2026 |
| Z Prime Ltd | Information & communication | 2013 |
| Z TEX Sampling Ltd | Manufacturing | 2018 |
| Z&A Property Holdings Ltd | Hospitality | 2025 |
| Z&F Corporation Ltd | Wholesale & retail | 2023 |
| Z&H Property Management Limited | Real estate | 2022 |
| Z3 Properties Ltd | Real estate | 2019 |
| Zaaar Limited | Real estate | 2024 |
| Zaal Perfect Services Limited | Wholesale & retail | 2022 |
| Zaandi Ltd | Transport & logistics | 2025 |
| Zacit Management Limited | Administrative & support | 2021 |
| ZAE Prop Ltd | Real estate | 2025 |
| Zahin Clothing and Footwear Ltd | Wholesale & retail | 2023 |
| Zahsam Limited | Professional & scientific | 2022 |
| Zaib Global Ltd | Wholesale & retail | 2025 |
| Zainullah Enterprise Limited | Wholesale & retail | 2024 |
| ZAK VIP Travels Ltd | Transport & logistics | 2023 |
| Zaki Consultancy Limited | Professional & scientific | 2023 |
| Zakiamazon Ltd | Wholesale & retail | 2024 |
| Zamok Tzarberg Gruppa Limited | Public administration | 2022 |
| Zapescu Ltd | Construction | 2024 |
| ZAR Fine Art & Illustration Ltd | Wholesale & retail | 2026 |
| Zassh Dent Supplies Limited | Manufacturing | 2025 |
| Zayra Retail Ltd | Wholesale & retail | 2026 |
| ZDB Global Logicare UK Limited | Transport & logistics | 2024 |
| Zeal Racing Limited | Arts & recreation | 2022 |
| ZEE Rock Ltd | Wholesale & retail | 2025 |
| Zeera Hayes Limited | Hospitality | 2025 |
| Zeera Trade (UK) Ltd | Hospitality | 2021 |
| Zehyn Ltd | Wholesale & retail | 2026 |
| Zeid Designs Ltd | Construction | 2015 |
| Zeina Atelier Ltd | Wholesale & retail | 2025 |
| Zeiz Ltd | Manufacturing | 2021 |
| Zelda Holdings Ltd | Real estate | 2024 |
| Zelda Properties Ltd | Real estate | 2024 |
| Zelena Limited | Professional & scientific | 2001 |
| ZEN Secure Ltd | Professional & scientific | 2024 |
| ZEN Shine Ltd | Administrative & support | 2024 |
| Zenitec Limited | Wholesale & retail | 2021 |
| Zenith Paramount Consumer Retail Limited | Wholesale & retail | 2026 |
| Zenithize Limited | Professional & scientific | 2025 |
| Zenova Financial Ltd | Professional & scientific | 2025 |
| Zentivate Ltd | Information & communication | 2025 |
| Zero Degrees Systems Ltd | Other services | 2016 |
| Zetaray Limited | Financial services | 2020 |