| World Bioprotection Research Foundation Ltd | Professional & scientific | 2023 |
| World Bioprotection Summit Ltd | Professional & scientific | 2019 |
| World's Finest Limited | Other services | 2024 |
| WP & RM Developments Ltd | Real estate | 2017 |
| WPB Ltd | Manufacturing | 2019 |
| WPB Racing Limited | Manufacturing | 2019 |
| WPB Welshpitbikes Ltd | Wholesale & retail | 2019 |
| WPS Property Services Limited | Real estate | 2020 |
| Wright & Phillips Carpentry & Building Limited | Manufacturing | 2012 |
| Writemedia Solutions Limited | Other services | 2011 |
| Wroxton Productions Limited | Information & communication | 2006 |
| WS Smile Studio Ltd | Health & social care | 2023 |
| WSB Properties Limited | Real estate | 2025 |
| WSP Direct Sales Ltd | Wholesale & retail | 2025 |
| WTR Consulting & Solutions Ltd | Professional & scientific | 2023 |
| Wundr Space Ltd | Information & communication | 2024 |
| Wurlnet Limited | Professional & scientific | 2017 |
| WV Stores Ltd | Wholesale & retail | 2019 |
| WVR (Wincanton) Ltd | Wholesale & retail | 2026 |
| Wwdmd Limited | Arts & recreation | 2019 |
| Wwscenics Holdings Ltd | Financial services | 2025 |
| Wwscenics Ltd | Manufacturing | 2011 |
| WXL Services Limited | Other services | 2018 |
| WYE Valley Pharmacy Ltd | Wholesale & retail | 2020 |
| Wyld Web Development Limited | Information & communication | 2014 |
| Wylde Green Ltd | Real estate | 2023 |
| Wyldflower Limited | Arts & recreation | 2020 |
| WYN Wood Limited | Agriculture & fishing | 2005 |
| Wyndham Conservative Club & Institute,Barry,Limited(The) | Hospitality | 1898 |
| Wynfyd Ltd | Real estate | 2021 |
| Wyser Ltd | Information & communication | 2020 |
| Wyser Ventures Ltd | Financial services | 2024 |
| X Engineering Limited | Professional & scientific | 2023 |
| X-Cel Security Ltd | Professional & scientific | 2005 |
| X-Treme Concept Ltd | Transport & logistics | 2018 |
| X4 Software Ltd | Wholesale & retail | 2013 |
| Xander Kostroma Fashion Ltd | Manufacturing | 2015 |
| Xecon Limited | Real estate | 1978 |
| Xena Services Ltd | Construction | 2016 |
| Xernecorn Limited | Professional & scientific | 2024 |
| Xeros Properties Ltd | Real estate | 2026 |
| Xinyuansd Limited | Real estate | 2020 |
| XL Aesthetics Ltd | Manufacturing | 2023 |
| XL Wales | Education | 1996 |
| XL: UK Radio Ltd | Information & communication | 2025 |
| XO Kinetics Limited | Wholesale & retail | 2016 |
| Xoconsult Limited | Professional & scientific | 2018 |
| Xpanza Ltd | Wholesale & retail | 2025 |
| Xpressions Studio Limited | Professional & scientific | 2008 |
| XRT Textiles Limited | Wholesale & retail | 2025 |
| Xtech Services Limited | Professional & scientific | 2015 |
| Xtravel Group Ltd | Administrative & support | 2023 |
| XYY Design & Build Ltd | Construction | 2025 |
| Y Awards Limited | Education | 2025 |
| Y Clwb Padel CYF | Arts & recreation | 2025 |
| Y Ddraig Ltd | Hospitality | 2020 |
| Y Gwachel Limited | Hospitality | 2017 |
| Y Hero Limited | Wholesale & retail | 2014 |
| Y Nyth CYF | Real estate | 2017 |
| Y.C.P. Limited | Professional & scientific | 1993 |
| Yachts.Co International Ltd | Wholesale & retail | 2007 |
| Yalla Property Solutions Ltd | Real estate | 2017 |
| Yallops of Mumbles Limited | Wholesale & retail | 2019 |
| Yamgo Ltd | Information & communication | 1998 |
| Yana Carwash Ltd | Health & social care | 2025 |
| YBL Collection Limited | Wholesale & retail | 2024 |
| YC Education Ltd | Education | 2026 |
| Yeadon Limited | Manufacturing | 1971 |
| Yellow Cabs 2020 Limited | Transport & logistics | 2019 |
| Yellow Cabs Limited | Transport & logistics | 2021 |
| Yellow Home Care Services Limited | Health & social care | 2025 |
| Yellowstar Trading Limited | Wholesale & retail | 2005 |
| Yessaian Ltd | Other services | 2021 |
| Yetland Limited | Wholesale & retail | 2005 |
| YFI Property Development Ltd | Households | 2026 |
| Yfory Ltd | Information & communication | 2009 |
| YG Creative Digital Ltd | Information & communication | 2026 |
| YG Cuisine Limited | Hospitality | 2024 |
| YIM Property 1 Ltd | Extraterritorial | 2001 |
| YJB Films Limited | Information & communication | 2013 |
| YJB Records Ltd | Information & communication | 2024 |
| YJD Limited | Health & social care | 2024 |
| YKG96 Limited | Wholesale & retail | 2025 |
| Ymarfer Music Ltd | Education | 2024 |
| Ymddiriedolaeth Penllergare - the Penllergare Trust | Arts & recreation | 2000 |
| Ynys-Y-Plant Management Company Limited | Households | 2001 |
| Yo-Cart Limited | Extraterritorial | 2014 |
| Yogaya CIC | Education | 2019 |
| Yolo Real Estate Ltd | Real estate | 2016 |
| Yons Digital Ltd | Information & communication | 2020 |
| Yorgun Ltd | Hospitality | 2019 |
| Yorgun Properties Ltd | Real estate | 2022 |
| York Chambers (Swansea) Ltd | Real estate | 2016 |
| York Court Management Company Limited | Households | 1983 |
| Yosief Araya Ltd | Extraterritorial | 2026 |
| Yotta Digital Ltd | Information & communication | 2019 |
| YOU 2.0 Ltd | Education | 2025 |
| YOU ARE My Sunshine Services Ltd | Public administration | 2019 |
| YOU Should NOT BE Limited | Extraterritorial | 2023 |
| Young Dragons CIC | Education | 2019 |