| Complete Circle Enterprises Limited | Administrative & support | 2020 |
| Complete Success Limited | Professional & scientific | 2017 |
| Composite Doors Cardiff Limited | Wholesale & retail | 2018 |
| Concept Fire & Electrical Ltd | Administrative & support | 2010 |
| Concept Mechanical Limited | Construction | 2019 |
| Conks Ltd | Manufacturing | 2025 |
| Connect Studies Limited | Administrative & support | 1998 |
| Conrad Asset Holdings Ltd | Financial services | 2026 |
| Conrad Estate Agents Ltd | Real estate | 2025 |
| Consultants in Design Limited | Professional & scientific | 1998 |
| Consulting LR Ltd | Administrative & support | 2024 |
| Control and Hazardous Specialists Limited | Wholesale & retail | 2019 |
| Cookies and Kreme Brothers Ltd | Hospitality | 2025 |
| Cooksey Landscape Gardening Ltd | Administrative & support | 2023 |
| Cooksey Property Group Ltd | Real estate | 2025 |
| Cooksey Renovation Ltd | Construction | 2022 |
| Cool Head Productions Ltd | Information & communication | 2004 |
| Copona Limited | Wholesale & retail | 2024 |
| Core Design Engineering Ltd | Professional & scientific | 2026 |
| Core Engineering Limited | Manufacturing | 2012 |
| Corepsych MED Ltd | Health & social care | 2026 |
| Corporate Instinct Limited | Professional & scientific | 2009 |
| Coslec Ltd | Construction | 2021 |
| Cosmic Painters Ltd | Construction | 2023 |
| Cosmos Serviced Apartments Ltd | Hospitality | 2018 |
| Countermax Ltd | Manufacturing | 1996 |
| Court Road 117 Lease Limited | Real estate | 2025 |
| COX & Hitchcock Dental Group Ltd | Health & social care | 2013 |
| CP Safety & Training Ltd | Other services | 2025 |
| Craft With ME C.I.C. | Health & social care | 2024 |
| Crafty Little Dragon Limited | Wholesale & retail | 2015 |
| Craig Crosbie Ltd | Real estate | 2014 |
| Crawford-Clarke Limited | Health & social care | 2009 |
| Creating Mortgage Solutions Limited | Financial services | 2020 |
| Creative Construction Ltd | Construction | 2023 |
| Creative Software Design Limited | Information & communication | 2010 |
| CRJ Group Limited | Construction | 2022 |
| Crosbie Bodley Limited | Health & social care | 2012 |
| Cross Street Motors Ltd | Wholesale & retail | 2023 |
| Crossland Trading Limited | Manufacturing | 2001 |
| Crossway-Brook Street Management Company Limited | Other services | 2002 |
| Crow's Nest Barry Island Ltd | Real estate | 2021 |
| CSR Plumbing & Heating Limited | Construction | 2025 |
| Cuckoo Dell Property Ltd | Real estate | 2024 |
| Curtain UP Theatre Company Ltd | Arts & recreation | 2023 |
| Curtis Barrett Ltd | Transport & logistics | 2024 |
| Cutc CIC | Arts & recreation | 2025 |
| CVE Aerospace Ltd | Manufacturing | 2019 |
| Cwfm Ltd | Manufacturing | 2024 |
| Cwmni Morgan CYF. | Financial services | 2026 |
| Cwmpasot Community Interest Company | Health & social care | 2022 |
| Cwtch Cleaning Limited | Other services | 2015 |
| Cwtche Ltd | Wholesale & retail | 2025 |
| Cymraeg Catering Limited | Administrative & support | 2007 |
| Cymraeg Vending Limited | Hospitality | 1997 |
| Cynefin at Fonmon Castle CIC | Other services | 2026 |
| Cynhyrchiadau Elsi Productions Limited | Information & communication | 2009 |
| Cynnydd CRM Ltd | Information & communication | 2026 |
| D & D Ladner Properties Ltd | Real estate | 2022 |
| D J W Medical Services Limited | Health & social care | 2017 |
| D K Stores Ltd | Wholesale & retail | 2018 |
| D&C Facade Solutions Ltd | Construction | 2025 |
| D&P Property Estates Limited | Real estate | 2022 |
| D&X Investments Ltd | Real estate | 2022 |
| D.C.I. Enterprises Europe Limited | Administrative & support | 2014 |
| D.R.C. Barry Ltd | Wholesale & retail | 2016 |
| Dabba Street Food Ltd | Hospitality | 2019 |
| Dalablast Ltd | Professional & scientific | 2025 |
| DAN and LIV Limited | Transport & logistics | 2018 |
| Dana Panciu Ltd | Health & social care | 2019 |
| Danieal’S Express Ltd | Hospitality | 2026 |
| Darlington Bros Limited | Construction | 2002 |
| Darren Bousie Property Maintenance Ltd | Households | 2023 |
| David Davies House (Freehold) Ltd | Real estate | 2025 |
| David Davies House RTM Ltd | Real estate | 2025 |
| David Evans Agricultural Limited | Wholesale & retail | 2002 |
| David Swallow Consulting Ltd. | Professional & scientific | 2013 |
| Davids Wharf Estate Ltd | Households | 2023 |
| Davies Brooks Property Ltd | Real estate | 2025 |
| Dawan Developments (Spider Camp) Limited | Construction | 2017 |
| Dawan Developments Limited | Real estate | 2013 |
| Dead Ball Analytics Limited | Information & communication | 2025 |
| Dead Bandit Ltd | Information & communication | 2024 |
| Deans Court (Rhoose) Limited | Hospitality | 1986 |
| DEM Crew Limited | Extraterritorial | 2022 |
| Dennis Hellyar Architects Limited | Professional & scientific | 2014 |
| Denworth Limited | Extraterritorial | 1989 |
| Desi Beats Dance Company Ltd | Education | 2023 |
| Designer Group Ltd | Wholesale & retail | 2016 |
| Desroches Management Ltd | Financial services | 2023 |
| Dessert 2026 Limited | Hospitality | 2026 |
| Desserttwala Ltd | Hospitality | 2025 |
| Develop UK Limited | Real estate | 1983 |
| Develop UK Northern Limited | Real estate | 2001 |
| Devon Place Limited | Health & social care | 2007 |
| Dewi White 154 Limited | Professional & scientific | 1990 |
| Dgaconstruct Ltd | Construction | 2021 |
| DH Engineering Tech Ltd | Professional & scientific | 2026 |
| Diamond Dusters Ltd | Administrative & support | 2026 |
| Diamond Shine Commercial Cleaning & Housekeeping Limited | Administrative & support | 2021 |