| Wootton Mooring Limited | Other services | 2023 |
| Workers Family Limited | Administrative & support | 2017 |
| Workforce FM Ltd | Administrative & support | 2024 |
| Workforce Paving Ltd | Construction | 2022 |
| Workingversion Ltd | Professional & scientific | 2020 |
| Workline Limited | Construction | 2015 |
| World Estates Limited | Construction | 1988 |
| World Film Services Limited | Information & communication | 1979 |
| World Group of Companies Limited | Professional & scientific | 1995 |
| World of Beds (Essex) Limited | Wholesale & retail | 2018 |
| Worldspan Living Limited | Administrative & support | 2020 |
| Worldview Capital Management LLP | | 2011 |
| Worldview Capital Services Ltd | Other services | 2011 |
| Worzel Scenery Ltd | Manufacturing | 2025 |
| WOW Recovery & Vehicle Hire Ltd | Wholesale & retail | 2024 |
| Wozz Limited | Administrative & support | 2023 |
| WP Feedback Ltd | Information & communication | 2019 |
| Wren Pictures Ltd | Information & communication | 2005 |
| Wright Property Management Limited | Other services | 2010 |
| Written Records Limited | Information & communication | 2015 |
| WS Builders Construction Ltd | Construction | 2022 |
| WSI Ltd | Professional & scientific | 2017 |
| WSR Property Investments Ltd | Real estate | 2026 |
| WTL Limited | Wholesale & retail | 2002 |
| WW Piam UK Limited | Real estate | 2020 |
| Wwff Consultants Ltd | Information & communication | 2024 |
| Wwmm Properties Ltd | Real estate | 2017 |
| Wymer Renewables Ltd | Construction | 2024 |
| Wyndcliffe Properties Limited | Real estate | 1963 |
| Wynter Creative Consultancy Limited | Professional & scientific | 2023 |
| X-Elex Ltd | Construction | 2022 |
| Xara Sportswear (UK) Limited | Wholesale & retail | 1989 |
| Xavier Gardening and Design Ltd | Administrative & support | 2013 |
| Xcelus Digital Ltd | Information & communication | 2016 |
| Xelle Ltd | Construction | 2020 |
| Xeron Consulting Limited | Professional & scientific | 2017 |
| XL London Ltd | Wholesale & retail | 2020 |
| Xpert Accounting Solutions Limited | Professional & scientific | 2025 |
| XPG Events Limited | Other services | 2004 |
| Xpress Print Limited | Information & communication | 2008 |
| Xprt Construction Limited | Construction | 2021 |
| Xscaler Ltd | Information & communication | 2026 |
| XTR Electric Ltd | Construction | 2022 |
| Xtreme Pursuits Limited | Arts & recreation | 2005 |
| Xtrix Limited | Professional & scientific | 2022 |
| Y Marks the Spot Ltd | Professional & scientific | 2019 |
| Y.C.L Enterprise Limited | Health & social care | 2019 |
| Y.C.L Entertainment Limited | Health & social care | 2022 |
| Yaar Bar Limited | Hospitality | 2018 |
| Yalber Limited | Financial services | 2016 |
| Yanev Decorating Services Ltd | Construction | 2018 |
| Yanev Decorative Finishings Ltd | Construction | 2024 |
| Yashvi Construction Limited | Construction | 2025 |
| YASIN12 Limited | Hospitality | 2024 |
| Yasla Limited | Administrative & support | 2019 |
| Yattsdale Flat Management Company Limited | Households | 1982 |
| Yavneh College Academy Trust | Education | 2011 |
| Yaya Creative Ltd | Information & communication | 2019 |
| Yazten Limited | Hospitality | 2019 |
| YBF Eyewear Limited | Wholesale & retail | 2024 |
| YCL Group Limited | Health & social care | 2023 |
| YCT Housing Services Ltd | Real estate | 2023 |
| YE Olde Traditional Furniture Co. Limited | Wholesale & retail | 1991 |
| Yellow MAT Company Ltd | Extraterritorial | 2009 |
| Yellow Oak Properties Ltd | Real estate | 2021 |
| Yellow Sunshine (UK) Ltd | Wholesale & retail | 2013 |
| Yellowcroft Limited | Other services | 2019 |
| Yemrold Limited | Real estate | 2005 |
| Yeranein Limited | Financial services | 2013 |
| YES Group International Limited | Information & communication | 2005 |
| YEW TR33 Limited | Hospitality | 2018 |
| YEW Tree Court (Elstree) Limited | Real estate | 1992 |
| YH Financial Solutions Ltd | Financial services | 2019 |
| Yianni Motors Limited | Wholesale & retail | 2018 |
| Ying Chen International Limited | Administrative & support | 2023 |
| Yingly Group UK Ltd | Wholesale & retail | 2018 |
| YMG Advisors Limited | Financial services | 2020 |
| Ymza Ltd | Health & social care | 2021 |
| YNR Trinaam Ltd | Information & communication | 2025 |
| YNY Properties Ltd | Real estate | 2024 |
| YOD Props Limited | Information & communication | 2023 |
| Yokai Media Ltd | Professional & scientific | 2021 |
| Yoke CNC Ltd | Construction | 2021 |
| Yoomco Ltd | Real estate | 2012 |
| York Props Ltd | Arts & recreation | 2021 |
| YOU Shout Ltd | Administrative & support | 2014 |
| Youlinmolin Limited | Hospitality | 2022 |
| Young Explorers @ Cobham Limited | Education | 2013 |
| Your Coffee Place Ltd | Hospitality | 2020 |
| Your Edge Solutions Limited | Professional & scientific | 2015 |
| Your Expert EYE Limited | Professional & scientific | 2019 |
| Your Eyes WE Care Ltd | Health & social care | 2020 |
| Your KIT London Ltd | Manufacturing | 2024 |
| Yourgames Ltd | Information & communication | 2025 |
| YSN Professional Cleaning Services Limited | Administrative & support | 2022 |
| YTR Homes Limited | Real estate | 2020 |
| YU Yang Limited | Hospitality | 2014 |
| Yucatan LDN Ltd | Other services | 2018 |
| Yunhan Limited | Manufacturing | 2016 |
| Yusuf Transport Limited | Transport & logistics | 2026 |