| Woofocus Limited | Information & communication | 2021 |
| Woolenstocks Limited | Manufacturing | 2005 |
| Woolford Trading Limited | Wholesale & retail | 2025 |
| Wordprism Ltd | Information & communication | 2025 |
| Workflowz Ltd | Information & communication | 2009 |
| Workmanco Limited | Arts & recreation | 2016 |
| Workshare Limited | Information & communication | 1998 |
| Workshare Technology Holdings Limited | Information & communication | 2010 |
| Worksmith Associates Limited | Professional & scientific | 2013 |
| World Golfers Championship Limited | Other services | 1996 |
| Worldwide Attractions Limited | Administrative & support | 2003 |
| Worldwide Education & Immigration Services Limited | Education | 2009 |
| Worsley VR Limited | Professional & scientific | 2010 |
| WOW Box Ltd | Hospitality | 2024 |
| Wowspot Ltd. | Information & communication | 2025 |
| WP Engine (UK) Limited | Professional & scientific | 2014 |
| Wraich Management Ltd | Real estate | 2019 |
| Write Pilot LLP | | 2011 |
| WSB Legal Limited | Professional & scientific | 2024 |
| WSS Consultancy Limited | Professional & scientific | 2017 |
| WTA Limited | Households | 2002 |
| WTR Management Services Ltd | Construction | 2023 |
| Wukong Food Limited | Hospitality | 2023 |
| Wursta Technology Holdings UK Limited | Information & communication | 2024 |
| WYE Valley Chamber Music | Arts & recreation | 2003 |
| Wylo Developments Limited | Construction | 2021 |
| Wyndham Road Management Ltd | Real estate | 2025 |
| Wyreit App Ltd | Information & communication | 2026 |
| X3 Property Ltd | Real estate | 2023 |
| Xaniglobal Ltd | Real estate | 2024 |
| Xbourse Global Ltd | Information & communication | 2020 |
| Xclusive Weddings Limited | Other services | 2005 |
| Xempo Limited | Wholesale & retail | 2010 |
| Xenex Advisory Limited | Information & communication | 2016 |
| Xerxes Properties Ltd | Real estate | 2025 |
| XH Brothers Builders Limited | Construction | 2022 |
| Xhosttellnet Limited | Administrative & support | 2005 |
| XIN Studio Ltd | Professional & scientific | 2016 |
| Xlsx Solutions Limited | Information & communication | 2013 |
| XP 2 PAY Limited | Professional & scientific | 2025 |
| XP Accountancy Services Limited | Professional & scientific | 2021 |
| XP Bookkeeping Services Limited | Professional & scientific | 2021 |
| XP Commercial Services Limited | Other services | 2021 |
| XP ID LAB Limited | Professional & scientific | 2021 |
| XP Investments Group Limited | Real estate | 2022 |
| XP Meta Limited | Information & communication | 2021 |
| XP Payroll Services Limited | Professional & scientific | 2021 |
| XP Rentals Ltd | Wholesale & retail | 2025 |
| XP Secretarial Services Limited | Professional & scientific | 2019 |
| Xp-Pay Limited | Professional & scientific | 2023 |
| XPD Limited | Other services | 1992 |
| Xperience Studios Ltd | Information & communication | 2022 |
| Xplus London Limited | Professional & scientific | 2014 |
| Xplus Studios Limited | Information & communication | 2021 |
| Xsellco UK Limited | Information & communication | 2017 |
| Xspectra Ltd | Information & communication | 2026 |
| Xtnea Ltd | Administrative & support | 2025 |
| XU Treasury Holdings Ltd | Administrative & support | 2023 |
| Xway Services Limited | Other services | 2016 |
| Xwells Energy Limited | Administrative & support | 2014 |
| Xwells Solutions Limited | Administrative & support | 2022 |
| Xylosys Security Solutions Limited | Information & communication | 2015 |
| Y Xologist Limited | Health & social care | 2024 |
| Y&Y Double Wins Ltd | Hospitality | 2024 |
| Yakuma Accountancy Limited | Professional & scientific | 2010 |
| Yammy Sushi Kingston Ltd | Wholesale & retail | 2022 |
| Yandia Car Rental Ltd | Wholesale & retail | 2014 |
| Yang&Young Education Ltd | Education | 2024 |
| Yaqeen Research UK | Other services | 2025 |
| Yaqi Ltd | Wholesale & retail | 2025 |
| Yard Sauna Ltd | Other services | 2025 |
| Yasmin Beauty Clinic Limited | Other services | 2023 |
| Yellow Tulips Ltd | Professional & scientific | 2025 |
| Yellow Zebra Travel Ltd | Administrative & support | 2012 |
| Yemster Limited | Information & communication | 2008 |
| Yeomans Keep Residents Company Limited | Households | 1969 |
| YES YES Tech Ltd | Professional & scientific | 2014 |
| Yesimkunter Limited | Administrative & support | 2012 |
| Yeternal Ltd | Wholesale & retail | 2026 |
| YH Financial Ltd. | Professional & scientific | 2017 |
| Yilai Management Ltd | Professional & scientific | 2023 |
| Yilmaz Construction Buildings Limited | Construction | 2024 |
| Yingwan Therapy Limited | Health & social care | 2018 |
| Yinson Production Offshore Holdings Ltd | Financial services | 2024 |
| Yinson Production Offshore Investments Ltd | Financial services | 2024 |
| Yiouc Limited | Other services | 2022 |
| YK Beauty Limited | Other services | 2000 |
| YM Translations & Consultancy Limited | Professional & scientific | 2016 |
| Yolo Group Restaurants Limited | Hospitality | 2024 |
| Yooz Global, Ltd. | Professional & scientific | 2016 |
| Yote Design Limited | Professional & scientific | 2012 |
| Your Accounts Accountancy Services Ltd | Professional & scientific | 2025 |
| Your Education Space Ltd | Professional & scientific | 2020 |
| Your Garden IS My Garden Ltd. | Wholesale & retail | 2021 |
| Your Hairdresser Limited | Other services | 2014 |
| Yourhousensupplyshop Ltd | Administrative & support | 2026 |
| Ysjoa Ltd | Hospitality | 2020 |
| Yung and Giupponi Ltd | Professional & scientific | 2023 |
| Yunova Limited | Wholesale & retail | 2025 |
| Yura Wasteman Limited | Other services | 2022 |