| Cfmaintenance Ltd | Manufacturing | 2025 |
| CG Tree Cutting Services Ltd | Agriculture & fishing | 2023 |
| CGP Transport Limited | Transport & logistics | 2016 |
| Chandlers Court Ltd. | Households | 1993 |
| Charlie Parker Management Ltd | Real estate | 2024 |
| Charliescommercial Limited | Wholesale & retail | 2019 |
| Charm Interiors Limited | Wholesale & retail | 2023 |
| Chase Contractors Ltd. | Construction | 1995 |
| Chaudhary Sons & Co Ltd | Wholesale & retail | 2025 |
| Cheatbites Limited | Hospitality | 2025 |
| Chemview Holdings Limited | Professional & scientific | 2017 |
| Chen Tomkinson Limited | Professional & scientific | 2026 |
| Chendalize Technology Customisation Co., Limited | Wholesale & retail | 2025 |
| Cherish Valley Care Ltd | Health & social care | 2025 |
| Chethemfoods Ltd | Manufacturing | 2026 |
| Chicken Cottage Pontypridd Limited | Hospitality | 2025 |
| China Yangzhou GUO TAI Co., Ltd | Wholesale & retail | 2013 |
| Chippie EM Building & Carpentry Ltd | Construction | 2025 |
| Chiya Barbers UK Ltd | Other services | 2021 |
| CHJ Carpentry & Design Ltd | Manufacturing | 2021 |
| Choices Express Ltd | Hospitality | 2019 |
| Chophora Holdings Limited | Extraterritorial | 2016 |
| Chowe Properties Ltd | Real estate | 2024 |
| Chris Davies Property Ltd | Real estate | 2021 |
| Chris Jeffreys Motors Ltd | Wholesale & retail | 2011 |
| Christopher Homes LLP | | 2023 |
| Church Village Barbers Ltd | Other services | 2025 |
| Chushuo UK Ltd | Wholesale & retail | 2026 |
| Cikana Fashion Company Ltd | Wholesale & retail | 2025 |
| Cinnamon Pontypridd Limited | Hospitality | 2024 |
| Circle Eight DNB Ltd | Arts & recreation | 2025 |
| Citadel Property Services Ltd | Construction | 2017 |
| Citrus Arts Limited | Arts & recreation | 2011 |
| City Burrow Ltd | Real estate | 2025 |
| CJ Fitouts Ltd | Construction | 2025 |
| CK Draft and Design Limited | Arts & recreation | 2026 |
| CL Support Ltd | Administrative & support | 2024 |
| Clare L Davies Ltd | Administrative & support | 2015 |
| Claremont Court Care Home Limited | Other services | 2012 |
| Class Waffle Pontypridd Ltd | Hospitality | 2024 |
| Classic Global Services Limited | Hospitality | 2007 |
| CLC Flooring Ltd | Construction | 2026 |
| Clean'D by Rosie Ltd | Administrative & support | 2023 |
| Cleaner Ovens Limited | Administrative & support | 2015 |
| Cleaner Windows Cardiff Ltd | Administrative & support | 2024 |
| Clear Stream Technology Ltd | Information & communication | 2006 |
| Clearview Windows Doors and Conservatories Ltd | Construction | 2018 |
| Clearviewwindowscardiff Cardiff LLC Limited | Construction | 2025 |
| CLJ Drylining Ltd | Construction | 2023 |
| Clode Innovations Ltd | Information & communication | 2025 |
| Clubs Automatics Limited | Professional & scientific | 1970 |
| CLY AMS Ltd | Wholesale & retail | 2023 |
| Clyde Business Ltd | Wholesale & retail | 2026 |
| CNR Building Services Ltd | Construction | 2021 |
| Coastal Retreats (Pembs) Ltd | Construction | 2018 |
| Coastline Builders (Southern) Limited | Construction | 2005 |
| Cobh Limited | Education | 2014 |
| Coelbren Ltd | Real estate | 2025 |
| Coffee & Cadence Limited | Hospitality | 2017 |
| Coform Limited | Extraterritorial | 2013 |
| Coform Secretaries Limited | Professional & scientific | 2010 |
| Coggins & Co Ltd | Other services | 2002 |
| COH Eateries Ltd | Hospitality | 2024 |
| Colin Downes Interior Services Limited | Construction | 2017 |
| Collins & Price Developments Limited | Construction | 2022 |
| Colsha Properties Limited | Real estate | 2025 |
| Commonwealth Capital Management Limited | Real estate | 2017 |
| Compassion & Liberty Care Limited | Professional & scientific | 2019 |
| Config R IT Limited | Information & communication | 2017 |
| Confix Drylining Limited | Construction | 2022 |
| Connective HR Limited | Professional & scientific | 2009 |
| Consortium Builders Ltd | Construction | 2020 |
| Contained Logistics Ltd | Transport & logistics | 2022 |
| Contibizz Ltd | Manufacturing | 2022 |
| Continental Corporate Care Logistics Ltd | Public administration | 2022 |
| Control Gear (Filtration) Limited | Manufacturing | 1980 |
| Control Gear (Group) Limited | Manufacturing | 1992 |
| Control Gear (Hydraulics) Limited | Wholesale & retail | 1986 |
| Control Gear Fluid Power Limited | Administrative & support | 1998 |
| Control Gear Limited | Manufacturing | 1973 |
| Coombes Electrical DC Ltd | Construction | 2025 |
| Core Strategic Land Ltd | Construction | 2016 |
| Coretemp Ltd | Energy | 2025 |
| Corevio Tech Ltd | Wholesale & retail | 2025 |
| Coreyblimey Limited | Arts & recreation | 2019 |
| Corie Wilde Limited | Professional & scientific | 2021 |
| Corner Cuts Barbers Limited | Other services | 2017 |
| Corner House Ltd | Hospitality | 2018 |
| Corral Investments Limited | Financial services | 2021 |
| Cortile Coffee Store Limited | Wholesale & retail | 2020 |
| Counter Force (CF Systems) CIC | Education | 2021 |
| CQ Project Engineering Ltd | Professional & scientific | 2026 |
| CR Salvage and Metals Ltd | Wholesale & retail | 2025 |
| Cr's Surveying & Commercial Management Services Ltd | Professional & scientific | 2019 |
| Craftcore Technology Ltd | Wholesale & retail | 2024 |
| Cragrose Limited | Professional & scientific | 2014 |
| Craig Geoservices Ltd | Professional & scientific | 2022 |
| Cramphorn Limited | Financial services | 2023 |
| CRB Coform Limited | Professional & scientific | 2014 |
| Created Entertainment Group Limited | Professional & scientific | 2026 |