| CW Cardiff Benefits Ltd | Administrative & support | 2022 |
| CW Estates Management Company Limited | Real estate | 2020 |
| CW Psychology Limited | Education | 2024 |
| CW Recruitment Ltd | Administrative & support | 2019 |
| CW Travels and Tours Limited | Administrative & support | 2025 |
| CW123 Limited | Extraterritorial | 2005 |
| Cwade Consulting Ltd | Professional & scientific | 2024 |
| Cwbic Ltd | Professional & scientific | 2017 |
| Cwch Limited | Real estate | 2012 |
| Cwcio Limited | Hospitality | 2018 |
| CWE Funding Projects Ltd | Financial services | 2015 |
| Cwfd Holding Ltd | Financial services | 2026 |
| Cwfj LLP | | 2025 |
| CWL Properties Limited | Real estate | 2003 |
| CWM Assets Limited | Financial services | 2025 |
| CWM Cwtch Healthcare Limited | Health & social care | 2023 |
| CWM Rhondda Waste Management Services Ltd | Water & waste | 2010 |
| Cwmbach Holdings Limited | Financial services | 2023 |
| Cwmbran Media Ltd | Information & communication | 2021 |
| Cwmdare House Cardiff Serviced Accommodation Ltd | Real estate | 2024 |
| Cwmdulais Dental Centre Limited | Health & social care | 2020 |
| Cwmni 29 Ltd | Information & communication | 2013 |
| Cwmni Canna Cyfyngedig | Professional & scientific | 2018 |
| Cwmni Caws Caerffili CYF. | Manufacturing | 2022 |
| Cwmni Eifion Limited | Information & communication | 2016 |
| Cwmni Glân CYF. | Administrative & support | 2015 |
| Cwmni Gwalia Limited | Real estate | 2014 |
| Cwmni Harp CYF | Information & communication | 2021 |
| Cwmni Rheoli Pentref Marina Conwy Cyfyngedig | Households | 1992 |
| Cwmni Stem Presents Ltd | Information & communication | 2023 |
| Cwmni Teledu Gweled / Gweled TV Ltd | Professional & scientific | 2016 |
| Cwrt Cefn House Management Company Limited | Real estate | 2007 |
| Cwrt Cefn Management Company Limited | Households | 1973 |
| Cwrt Cefn Road Company Limited | Households | 2023 |
| Cwrt Dewi Sant Cardiff Management Company Limited | Households | 2002 |
| Cwrt Glas Limited | Households | 2025 |
| Cwrt Graig Management Limited | Real estate | 1993 |
| Cwrt Iorweth Management Company Limited | Real estate | 2006 |
| Cwrt Penhill (Management) Limited | Households | 2015 |
| Cwrt Soffia Owners Limited | Households | 2021 |
| Cwrt ST Ioan Management Company (Cardiff) Limited | Real estate | 2021 |
| Cwrt Y Parc Management Company Limited | Real estate | 1991 |
| Cwrt-Y-Parc Limited | Real estate | 2003 |
| Cwsgroup Ltd | Financial services | 2019 |
| Cwtch & Code Ltd | Information & communication | 2025 |
| Cwtch Childcare & Nurseries Limited | Health & social care | 2019 |
| Cwtch Health Ltd | Professional & scientific | 2025 |
| Cwtchie Ltd | Wholesale & retail | 2021 |
| Cwtsh Nursery Limited | Education | 2014 |
| CXB Limited | Education | 2023 |
| CXO Foundry Limited | Professional & scientific | 2020 |
| Cyaibotics Ltd | Information & communication | 2018 |
| Cyan Consulting Limited | Information & communication | 2024 |
| Cyan East International Trading Co., Ltd | Extraterritorial | 2019 |
| Cybata Ltd | Professional & scientific | 2015 |
| Cyber Access Ltd | Information & communication | 2017 |
| Cyber Care Ltd | Information & communication | 2025 |
| Cyber Innovation Hub Ltd | Administrative & support | 2025 |
| Cyber NET Security Ltd | Information & communication | 2023 |
| Cyber Oasis Limited | Wholesale & retail | 2025 |
| Cyber Operations Management Limited | Wholesale & retail | 2017 |
| Cyber Platforms Ltd | Information & communication | 2019 |
| Cyber Protocol Services Ltd | Information & communication | 2025 |
| Cyber Psychology Security Essentials Ltd | Professional & scientific | 2020 |
| Cyber Risk Analytical Methods Ltd | Information & communication | 2026 |
| Cyber Security Measures Ltd | Information & communication | 2018 |
| Cybercentric Ltd | Information & communication | 2010 |
| Cybercloud Solutions Ltd | Information & communication | 2022 |
| Cyberdes Ltd | Information & communication | 2025 |
| Cyberhq Technologies Ltd | Information & communication | 2022 |
| Cyberline Trade Limited | Manufacturing | 2025 |
| Cybermind Consult Ltd | Information & communication | 2025 |
| Cyberskinz Limited | Information & communication | 2025 |
| Cybex Security Ltd | Manufacturing | 2019 |
| CYC Property Management Ltd | Real estate | 2021 |
| Cyclone Blue Limited | Professional & scientific | 2018 |
| CYCLONE24 Limited | Arts & recreation | 2016 |
| Cyclopaedia Limited | Wholesale & retail | 2003 |
| Cycnus Ltd | Wholesale & retail | 2022 |
| Cyfreithwyr Ledled Y Wlad CYF | Professional & scientific | 2014 |
| Cyhoeddi Cymru CYF | Information & communication | 2021 |
| Cylabs UK Limited | Information & communication | 2018 |
| Cylentrix Ltd | Wholesale & retail | 2025 |
| Cymorth (Cymru) | Other services | 2004 |
| Cymrai Software Solutions Limited | Professional & scientific | 2025 |
| Cymric Building Preservation Trust | Construction | 1985 |
| Cymric Property Company Limited | Real estate | 1959 |
| Cymru Care Limited | Administrative & support | 2007 |
| Cymru Properties Limited | Real estate | 2004 |
| Cymway Ltd | Other services | 2024 |
| Cynamonek Ltd | Wholesale & retail | 2025 |
| Cyncoed Cctv Ltd | Administrative & support | 2021 |
| Cyncoed Dental Practice Ltd | Health & social care | 2019 |
| Cyncoed Development Co Limited | Construction | 2014 |
| Cyncoed Gardens (Cardiff) Management Company Limited | Households | 2004 |
| Cyncoed Place Properties Limited | Real estate | 2025 |
| Cyncoed Property (Cardiff) Limited | Construction | 2005 |
| Cyncoed Property (Leisure) Ltd | Real estate | 2023 |
| Cyncoed Property Limited | Real estate | 1997 |
| Cynefin Films Limited | Information & communication | 2022 |