| CLS Ventilation Ltd | Construction | 2026 |
| Club 7 Summits Limited | Extraterritorial | 2004 |
| Club ALP 4000 Ltd | Extraterritorial | 1992 |
| Clwb Cariad Limited | Health & social care | 2025 |
| Clwb Ffoto Ltd | Professional & scientific | 2024 |
| Clydecatalyst Ltd | Professional & scientific | 2026 |
| Clydes Properties Ltd | Real estate | 2020 |
| Clytha Estates Limited | Real estate | 2020 |
| Clytha Farms Limited | Agriculture & fishing | 1996 |
| Clytha Square Ltd | Real estate | 2022 |
| Clytha Square Residents Association Limited | Households | 1995 |
| CM Gardening Ltd | Construction | 2024 |
| CM Management Group Ltd | Professional & scientific | 2015 |
| CM1 Limited | Construction | 2025 |
| CM11 Promotions Ltd | Arts & recreation | 2024 |
| CMA HR Limited | Administrative & support | 2019 |
| CMB Design and Build Ltd | Professional & scientific | 2021 |
| CMB Design and Management Limited | Professional & scientific | 2016 |
| CMB Services Ltd | Construction | 2015 |
| CMB Traffic Management Ltd | Construction | 2023 |
| CMC Partnership Consultancy Ltd | Professional & scientific | 2018 |
| Cmjd Pubs Ltd | Hospitality | 2025 |
| CMR Capital Ltd | Financial services | 2024 |
| CMR Properties Ltd | Real estate | 2025 |
| CMT Consulting UK Limited | Professional & scientific | 2003 |
| CN Survey Limited | Construction | 2014 |
| CNG Construction Ltd | Construction | 2019 |
| CNS Automotive Ltd | Transport & logistics | 2024 |
| COA Accounting Services Limited | Professional & scientific | 2025 |
| Coached by Cece Ltd | Other services | 2024 |
| Coachhouse Management Company Limited(The) | Households | 1986 |
| Coaching Footprint Ltd | Education | 2020 |
| Coachkit Group Limited | Information & communication | 2024 |
| Coast and Country Escapes Ltd | Hospitality | 2022 |
| Coastal Inns and Taverns Limited | Hospitality | 2001 |
| Cobalt Aerospace Group Ltd | Financial services | 2019 |
| Cobalt Aerospace Limited | Manufacturing | 2013 |
| Cobb Builders Ltd | Construction | 2024 |
| Cocanevie Ltd | Real estate | 2025 |
| Cocks Family Developments Limited | Real estate | 2024 |
| Coco Gardens & Landscaping Ltd | Construction | 2026 |
| Coconut Consultants Ltd | Information & communication | 2009 |
| Cocowaxmelts Ltd | Wholesale & retail | 2025 |
| Cod-Piece Limited | Real estate | 2003 |
| Coda Music and Education Ltd | Education | 2025 |
| Coded Welding Solutions Ltd | Professional & scientific | 2023 |
| Codefinders Ltd | Information & communication | 2020 |
| Codepecker Digital Ltd | Information & communication | 2025 |
| Codeweld Limited | Manufacturing | 2024 |
| Codi Consulting Limited | Professional & scientific | 2024 |
| Codi Crafted by Hand Ltd | Wholesale & retail | 2025 |
| Codi Development Limited | Construction | 2019 |
| Codi Renewables Limited | Professional & scientific | 2011 |
| Codi Trust Limited | Hospitality | 2013 |
| Codicollective Ltd | Information & communication | 2026 |
| Codtunzhub Ltd | Health & social care | 2024 |
| Coed Organic Ltd | Agriculture & fishing | 2018 |
| Coed Y Paen LLP | | 2016 |
| Coeliacs in Safe Hands CIC | Public administration | 2025 |
| Coffee at 26 Limited | Hospitality | 2023 |
| Coffee Corner (Newport) Limited | Hospitality | 2021 |
| Coffee Thirst Newport Limited | Hospitality | 2019 |
| Coffers & Co. Ltd | Financial services | 2026 |
| Coghlan Holdings Limited | Extraterritorial | 2019 |
| Cognisess Limited | Information & communication | 2011 |
| Cohesive Communications (Holdings) Limited | Professional & scientific | 2005 |
| Cohesive Communications Limited | Extraterritorial | 1998 |
| Cohlord Limited | Extraterritorial | 2010 |
| Coin OP Laundrette Limited | Other services | 2025 |
| Cojaluzo Ltd | Hospitality | 2018 |
| Colclough Plumbing and Heating Limited | Construction | 2018 |
| Coldra Consultancy Ltd | Administrative & support | 2017 |
| Coldra Productions Limited | Arts & recreation | 2026 |
| Cole's GIN Ltd | Manufacturing | 2020 |
| Coleman Property Management Limited | Extraterritorial | 2004 |
| Colesgreenwood Ltd | Real estate | 1994 |
| Coley Mill Management Limited | Administrative & support | 2004 |
| Colin Powell Carpentry & Kitchens Ltd | Construction | 2009 |
| Collabify Ltd | Information & communication | 2021 |
| Collatio-Bks LLP | | 2016 |
| Collective Resilience Ltd | Professional & scientific | 2025 |
| Collessie Ltd | Professional & scientific | 2017 |
| Colligan House (Management Company) Limited | Households | 1989 |
| Collingbourne Properties Ltd | Real estate | 2018 |
| Collins & Co Ltd. | Professional & scientific | 1999 |
| Collins Goodall Limited | Real estate | 1998 |
| Colmix Contractors Limited | Professional & scientific | 2001 |
| Color Steels Limited | Manufacturing | 2022 |
| Color-Clad Fabrications Limited | Manufacturing | 2024 |
| Colour Carsmetic Limited | Wholesale & retail | 2003 |
| Colour Coat Flashings Ltd | Manufacturing | 2025 |
| Colour Steels Limited | Manufacturing | 2022 |
| Colourfence Limited | Construction | 2005 |
| Colourwheel Cardiff Limited | Education | 2025 |
| Coltman Chiropractic Limited | Health & social care | 2005 |
| Columba Club Ltd | Hospitality | 2024 |
| Columbus Forty Five Limited | Financial services | 2016 |
| Comar Systems Ltd | Manufacturing | 2015 |
| Combesgate Limited | Financial services | 2010 |
| Combined Strength Training System Limited | Health & social care | 2022 |