| Composite Doors South Wales Limited | Construction | 2025 |
| Compressor Solutions Ltd | Manufacturing | 2012 |
| Compton Developments Limited | Construction | 1973 |
| Compton Group Limited | Construction | 2016 |
| Compton Insurance Services Limited | Financial services | 1992 |
| Compton Investment Management Limited | Financial services | 2025 |
| Compton Property Management Limited | Real estate | 1962 |
| Computech Services Limited | Real estate | 1993 |
| Computer Station (Cymru) Ltd | Information & communication | 2007 |
| Computeraid Limited | Professional & scientific | 1988 |
| Computers UN Limited | Extraterritorial | 2013 |
| Comsave Limited | Administrative & support | 2007 |
| Comzoo Ltd | Transport & logistics | 2016 |
| Comzoo Transport Ltd | Transport & logistics | 2025 |
| Concept BN Cymru Limited | Administrative & support | 2025 |
| Concept Carpentry Solutions Ltd | Construction | 2016 |
| Concept Ingredients Ltd | Extraterritorial | 2017 |
| Concept Project Services Limited | Construction | 2002 |
| Concordia Pharmacy Limited | Wholesale & retail | 2025 |
| Concustodio Risk Ltd | Financial services | 2022 |
| Conde Holdings Limited | Financial services | 2026 |
| Conifers From Hell Ltd | Administrative & support | 2011 |
| Connected Electric Ltd | Construction | 2022 |
| Conscious Consumer Collective Ltd | Wholesale & retail | 2019 |
| CONSCIOUSCOLLECTIVE1111 Ltd | Wholesale & retail | 2023 |
| Conservative Developments Limited | Construction | 2012 |
| Construction Engineering Consultants Limited | Professional & scientific | 2003 |
| Construction Repairs (Europe) Limited | Wholesale & retail | 1996 |
| Construction Repairs Limited | Construction | 2010 |
| Consult Coates Limited | Information & communication | 2025 |
| Consultancy UN Limited | Extraterritorial | 2014 |
| Container Conversions Limited | Professional & scientific | 2024 |
| Conte Davies & Co Ltd | Professional & scientific | 2003 |
| Contextual Systems Limited | Information & communication | 2006 |
| Contor Engineering Limited | Professional & scientific | 2023 |
| Contracked Ltd | Professional & scientific | 2022 |
| Contracting Solutions International Ltd | Administrative & support | 2023 |
| Cook Limited | Information & communication | 1995 |
| Coola Camper Co Ltd | Manufacturing | 2021 |
| Coombs Connected Ltd | Construction | 2024 |
| Coombs Land Surveys Ltd | Construction | 2023 |
| Cooperating System Ltd | Information & communication | 2025 |
| Copa Consulting Limited | Real estate | 2005 |
| Copper Bar Ltd | Hospitality | 2019 |
| Copper Coast Ltd | Construction | 2021 |
| Copper Court Limited | Real estate | 2015 |
| Copper Crwst Ltd | Hospitality | 2025 |
| Copper Pipe Supply Limited | Wholesale & retail | 2007 |
| Copper Rocket Books Ltd | Wholesale & retail | 2023 |
| Copperopolis Coffee Ltd | Manufacturing | 2025 |
| Copperstone Financial Services Limited | Financial services | 2005 |
| Copr Bay Consulting Limited | Professional & scientific | 2024 |
| Copr Contracts Ltd | Construction | 2024 |
| Coproduction Consultancy Limited | Professional & scientific | 2017 |
| COR Watersports Ltd | Arts & recreation | 2016 |
| Coracle Property Ltd | Real estate | 2020 |
| Coral Formwork Limited | Construction | 2009 |
| Corbec Installations Ltd | Construction | 2025 |
| Corbsco Limited | Information & communication | 2019 |
| Cordatus Limited | Professional & scientific | 2019 |
| Core Body Clinic Limited | Health & social care | 2014 |
| Corelo Ltd | Wholesale & retail | 2025 |
| Corey Young Bricklaying Limited | Construction | 2022 |
| Corking Idea Ltd | Wholesale & retail | 2018 |
| Corlan Limited | Professional & scientific | 2026 |
| Corner Park Garage Limited | Wholesale & retail | 2026 |
| Corner Park Limited | Wholesale & retail | 2024 |
| Corner Plot Holdings Limited | Construction | 2020 |
| Cornerstone Church Swansea | Other services | 2008 |
| Cornerstone Community Church (Wales) | Other services | 2012 |
| Cornerstone Equity Group Ltd | Construction | 2025 |
| Cornerstone Properties SW Ltd | Real estate | 2024 |
| Cornerstone Property Services Limited | Real estate | 2002 |
| Coron Limited | Administrative & support | 2013 |
| Corpath Group Limited | Administrative & support | 2022 |
| Corun Associates Limited | Professional & scientific | 2013 |
| Cosgrove Brown Commercial Limited | Financial services | 2014 |
| Cosgrove Brown Financial Planning Ltd | Financial services | 2011 |
| Cosi Care Ltd | Professional & scientific | 2018 |
| Cosmedicfx Limited | Other services | 2013 |
| Cosmedicplan Limited | Financial services | 2019 |
| Cosmetic Sculptor Ltd | Health & social care | 2012 |
| Cosmic Lifestyle UK Ltd | Hospitality | 2018 |
| Cosy Co Property Partners Ltd | Real estate | 2025 |
| Cosy CUB Games Limited | Manufacturing | 2022 |
| Coteglade Limited | Extraterritorial | 1973 |
| Cothi Harvesting Ltd | Agriculture & fishing | 2024 |
| Cotswold Rooms & Wellbeing Ltd | Construction | 2025 |
| Cottey Florist Limited | Wholesale & retail | 2022 |
| Cottleys Holdings Limited | Real estate | 2022 |
| Cotton & Sons Cleaning Supplies Ltd | Wholesale & retail | 2022 |
| Countrywide Hearing Limited | Health & social care | 2012 |
| Countrywide Tax Returns Limited | Professional & scientific | 2012 |
| County Contracts Flooring Limited | Administrative & support | 2017 |
| County House Limited | Real estate | 2022 |
| Coupleagolfers Ltd | Arts & recreation | 2025 |
| Courage in Community CIC | Education | 2025 |
| Course and Crest Ltd | Wholesale & retail | 2024 |
| Courtenay Price and Hill Limited | Real estate | 1982 |
| Courtney Haynes Tattoo Ltd | Other services | 2025 |