| Colcom International Ltd | Financial services | 2020 |
| Cold Call Forge Ltd | Professional & scientific | 2025 |
| Cold Email Secrets Ltd | Information & communication | 2025 |
| Colden Larch Limited | Health & social care | 2009 |
| Coldly Fire Ltd | Wholesale & retail | 2025 |
| Coldstream Air Conditioning Limited | Construction | 1998 |
| Cole Air Conditioning Services Ltd | Construction | 2024 |
| Cole Contractors Cardiff Limited | Water & waste | 2000 |
| Colenso Construction Limited | Wholesale & retail | 2006 |
| Coleo Ltd | Administrative & support | 2018 |
| Coles Funeral Directors Ltd | Other services | 2006 |
| Coles Group Limited | Professional & scientific | 2019 |
| Coles Mechanical Limited | Professional & scientific | 2025 |
| Coleson Consultants Limited | Information & communication | 2015 |
| Colevest Limited | Wholesale & retail | 2019 |
| Colgar Energy Ltd | Professional & scientific | 2023 |
| Colin Mccubbin Limited | Health & social care | 2009 |
| Colin Morgan T/A Cardiff Mortgage Centre Ltd | Extraterritorial | 2016 |
| Colin Paul Insulation Ltd | Other services | 2023 |
| Colin Rees Limited | Health & social care | 2026 |
| Colin Richardson Contractors Ltd | Construction | 2013 |
| Colindale Roofing and Building Ltd | Construction | 2026 |
| Colivia UK Limited | Administrative & support | 2022 |
| Collabfluence Ltd | Professional & scientific | 2025 |
| COLLABOR8 Ltd | Professional & scientific | 2021 |
| Collabx Limited | Construction | 2021 |
| Collar Club Cardiff and Vale Ltd | Agriculture & fishing | 2022 |
| Collect UK Ltd | Extraterritorial | 2016 |
| Collective Crowd Management Ltd | Administrative & support | 2021 |
| Collectors Lobby Limited | Wholesale & retail | 2025 |
| College Fields Close Residents (Barry) Management Company Limited | Households | 1990 |
| College of Healthcare Innovations Ltd | Construction | 2015 |
| College of Suffolk | Education | 2019 |
| Colleges Wales / Colegau Cymru Limited | Education | 1993 |
| Collekt Marketplace Ltd | Wholesale & retail | 2025 |
| Collens Healthcare (Southern) CYF | Health & social care | 2024 |
| Collier Creations & Civils Limited | Construction | 2025 |
| Collier Eatery Limited | Hospitality | 2019 |
| Collingwood Plumbing Ltd | Construction | 2026 |
| Collins & Wise Property Management Ltd | Real estate | 2017 |
| Collins Canine Company Ltd | Financial services | 2024 |
| Collins Creative Consulting Ltd | Professional & scientific | 2011 |
| Cololo Ltd | Hospitality | 2023 |
| Colonia Consulting Limited | Administrative & support | 2009 |
| Colony Estate and Finance Consultancy Ltd | Real estate | 2025 |
| Colored Gemstone Research Laboratory Limited | Manufacturing | 2022 |
| Colorfoto Limited | Professional & scientific | 1995 |
| Colorful IT Service Ltd | Information & communication | 2025 |
| Colorpoint Ltd | Administrative & support | 2002 |
| Colosseum Gym Cardiff Ltd | Arts & recreation | 2025 |
| Colossus Capital Limited | Real estate | 2018 |
| Colour Black Lighting Limited | Professional & scientific | 2007 |
| Colour Features Limited | Arts & recreation | 1996 |
| Colour Life Limited | Wholesale & retail | 2019 |
| Colour Wang Limited | Information & communication | 2021 |
| Colourclad Ltd | Construction | 2017 |
| Colours Connected Ltd | Arts & recreation | 2020 |
| Coltrun Limited | Financial services | 2016 |
| Colucci Estates Limited | Real estate | 2016 |
| Columba Properties Ltd | Construction | 2023 |
| Columba Water Engineering Ltd | Water & waste | 2026 |
| Columbus & C PLC | Information & communication | 2020 |
| Columbus Forty Four Limited | Other services | 2016 |
| Columbus Wood LLC Limited | Administrative & support | 2024 |
| Column Buildings Property Co Limited | Real estate | 2026 |
| Colver Structural Limited | Professional & scientific | 2006 |
| COM Software Ltd | Information & communication | 2014 |
| Combat Security Group Ltd | Administrative & support | 2019 |
| Combattivo Limited | Wholesale & retail | 2019 |
| Combglow Limited | Wholesale & retail | 2025 |
| Combine AI Limited | Information & communication | 2017 |
| Combined Electrical Solutions Limited | Construction | 2011 |
| Combined Technical Solutions Group Ltd | Administrative & support | 2026 |
| Comc Limited | Households | 2018 |
| Come AS YOU ARE Enterprise Ltd | Manufacturing | 2019 |
| Comebeauty Ltd | Wholesale & retail | 2024 |
| Comeio Limited | Wholesale & retail | 2020 |
| Comerford&Son Ltd | Professional & scientific | 2024 |
| Comet Clinical Limited | Professional & scientific | 2026 |
| Cometgold Limited | Other services | 2004 |
| Comewegrow Ltd | Wholesale & retail | 2022 |
| Comficab Ltd | Transport & logistics | 2024 |
| Comforself Health Foods Limited | Extraterritorial | 2020 |
| Comfort Care Homes Limited | Health & social care | 2004 |
| Comfort Craft Ltd | Wholesale & retail | 2025 |
| Comfort Property Investments Ltd | Real estate | 2022 |
| Comfort Sight Ltd | Wholesale & retail | 2026 |
| Comforters Care International Ltd | Health & social care | 2022 |
| Comfynest.Store Ltd | Wholesale & retail | 2024 |
| Comic CON Wales Ltd | Professional & scientific | 2018 |
| Comic Guru Limited | Wholesale & retail | 2009 |
| Comic Toolbox Ltd | Wholesale & retail | 2014 |
| Comlegals Ltd | Professional & scientific | 2024 |
| Comm-Tech IT Ltd | Information & communication | 2018 |
| Commercial & Contract Services (Wales) Ltd | Professional & scientific | 2025 |
| Commercial & Industrial Cleaning Ltd | Administrative & support | 2025 |
| Commercial Capital Partners Ltd | Financial services | 2024 |
| Commercial Cleaning Contractors Ltd | Households | 2015 |
| Commercial Energy Alliance Ltd | Wholesale & retail | 2019 |
| Commercial Facilities South Wales Ltd | Administrative & support | 2023 |