| Willow Lets Ltd | Real estate | 2022 |
| Willows Finance Limited | Financial services | 2008 |
| Wills Haulage Ltd | Transport & logistics | 2015 |
| Wilson COX Properties Ltd | Real estate | 2025 |
| Wilsonion Investments | Financial services | 2015 |
| Wind Direct Limited | Energy | 2010 |
| Windmills & Wellies Limited | Health & social care | 2015 |
| Windoor Services South Wales Limited | Manufacturing | 2016 |
| Windpower Parts Ltd | Manufacturing | 2025 |
| Winmau Dartboard Company Limited | Manufacturing | 1959 |
| Wisecote Limited | Extraterritorial | 2026 |
| Wisemove Estate and Lettings Agents (Bridgend) Ltd | Real estate | 2021 |
| Wiseward Limited | Construction | 2025 |
| Wish Events Limited | Extraterritorial | 2011 |
| Wishbone and Comb Ltd | Other services | 2025 |
| Wishes and Memories Ltd | Information & communication | 2024 |
| With a Clasp Limited | Manufacturing | 2025 |
| Without a Clasp Limited | Manufacturing | 2025 |
| WL Squared Limited | Professional & scientific | 2009 |
| Woffer Ltd | Information & communication | 2016 |
| Woffl Limited | Extraterritorial | 2014 |
| WOK 508 Limited | Hospitality | 2023 |
| Wolf Productivity Limited | Professional & scientific | 2019 |
| Wolframite Investments Ltd. | Real estate | 1996 |
| Womweb Limited | Information & communication | 2009 |
| Woodblake Consultants Limited | Professional & scientific | 2022 |
| Woodburn Installations Limited | Construction | 2018 |
| Woodfellas Bespoke Design Limited | Manufacturing | 2022 |
| Woodmore Limited | Extraterritorial | 2026 |
| Woodrate Limited | Extraterritorial | 2026 |
| Woodsmen Ltd | Agriculture & fishing | 2022 |
| Workare Limited | Health & social care | 2002 |
| Working Agent Ltd | Information & communication | 2024 |
| World Guard Limited | Other services | 2022 |
| World Masters Limited | Professional & scientific | 2000 |
| Worldwidepropertiesunlimited Ltd. | Real estate | 2020 |
| Worthington Roofers & Builders Limited | Construction | 2008 |
| WOW Properties Limited | Construction | 2001 |
| WRT Solutions Limited | Wholesale & retail | 2019 |
| WS Hayward Ltd | Real estate | 2023 |
| WSW Roofing Contractors Ltd | Construction | 2025 |
| Wyndham Commercial Properties Limited | Real estate | 1961 |
| WZC NCT Ltd | Hospitality | 2024 |
| X H Limited | Hospitality | 2010 |
| Xabier & Ocean Limited | Real estate | 2022 |
| Xanadu Events Ltd | Arts & recreation | 2014 |
| Xcape Limited | Construction | 2017 |
| Xolaninikelwa Ltd | Health & social care | 2023 |
| XY Automation Ltd | Wholesale & retail | 2017 |
| Y C Plastics Manufacturing Ltd | Manufacturing | 2014 |
| Y Cwtch Ltd | Arts & recreation | 2023 |
| Yacht Yard Ltd | Wholesale & retail | 2025 |
| Yardacre Limited | Information & communication | 2024 |
| Yardarch Limited | Extraterritorial | 2025 |
| Yardbray Limited | Extraterritorial | 2025 |
| Yardcare Limited | Extraterritorial | 2024 |
| Yardrise Limited | Extraterritorial | 2026 |
| Yavin Prime Ltd | Construction | 2022 |
| Ygeia Limited | Health & social care | 2021 |
| Ymgynghoraeth J Consulting Limited | Professional & scientific | 2019 |
| Ymgynghorwyr Lisk & Jones CYF | Professional & scientific | 2003 |
| Ynni Llety CYF | Energy | 2015 |
| Ynni Powys Ltd | Water & waste | 2025 |
| Ynyscynon Park (Management) Limited | Real estate | 2011 |
| Yonam Limited | Public administration | 2023 |
| Young & Digital Ecom Ltd | Wholesale & retail | 2025 |
| Your HR Ltd | Administrative & support | 2014 |
| YU Yuan Limited | Hospitality | 2020 |
| Yvettes Soblesspeart Limited | Health & social care | 2013 |
| Z J Pubs Ltd | Hospitality | 2025 |
| Zachariassen Limited | Extraterritorial | 2022 |
| Zanayi Limited | Health & social care | 2025 |
| Zato UK Limited | Manufacturing | 2012 |
| Zealmate Limited | | 1969 |
| Zebra Vehicles Limited | Wholesale & retail | 2020 |
| Zella Construction Limited | Construction | 2024 |
| Zella Corporation Limited | Construction | 2017 |
| Zentra Platforms Ltd | Information & communication | 2026 |
| Zero One Procurement Ltd | Extraterritorial | 2025 |
| Zero-E Global Limited | Professional & scientific | 2025 |
| Zerocote Limited | Extraterritorial | 2025 |
| Zeromead Limited | Construction | 2025 |
| Zerooneaiuk Limited | Information & communication | 2026 |
| Zeroward Limited | Administrative & support | 2024 |
| Zezo Property Ltd | Administrative & support | 2022 |
| Zone 1 Electric Motors Limited | Wholesale & retail | 2009 |
| Zonewhirl Limited | Agriculture & fishing | 1981 |
| Zxfx Ltd | Other services | 2019 |