| Celtic Coast Fish Company Limited | Manufacturing | 2016 |
| Celtic Couriers Holdings Limited | Transport & logistics | 2015 |
| Celtic Couriers Limited | Transport & logistics | 2005 |
| Celtic Gates Ltd | Construction | 2025 |
| Celtic Green Energy Ltd | Construction | 2013 |
| Celtic Instrumentation Ltd | Manufacturing | 1995 |
| Celtic Laser Ltd | Arts & recreation | 2012 |
| Celtic Oak Flooring Limited | Manufacturing | 2015 |
| Celtic Power Ltd | Professional & scientific | 2024 |
| Celtic Pride Limited | Agriculture & fishing | 2005 |
| Celtic Property Investments Ltd | Real estate | 2020 |
| Celtic Ready MIX Limited | Manufacturing | 2009 |
| Celtic Rendering Systems Limited | Construction | 2008 |
| Celtic Skills Limited | Administrative & support | 2023 |
| Celtic Therapy & Rehab Services Ltd | Professional & scientific | 2021 |
| Celtic Upvc Ltd | Manufacturing | 2022 |
| Celtic Warriors Ltd | Education | 2023 |
| Celtica Foods Limited | Manufacturing | 2002 |
| Celtwood Ltd | Construction | 2018 |
| Ceri Jones Plastering Ltd | Construction | 2024 |
| Cernon Creative Limited | Professional & scientific | 2009 |
| Cetma Ltd | Wholesale & retail | 2008 |
| CEZ House Ltd | Real estate | 2025 |
| CFJ Developments Ltd | Construction | 2024 |
| Champion Transport Ltd | Transport & logistics | 2025 |
| Chance Wales Support Group Limited | Health & social care | 2024 |
| Chap-Hill Outdoor Refurb Ltd | Administrative & support | 2018 |
| Chapter and FOX Ltd | Information & communication | 2025 |
| Charlene Davies Development Ltd | Construction | 2014 |
| Charles Gray Engineering Ltd | Manufacturing | 2019 |
| Cheers Event & Bar Services Ltd | Hospitality | 2015 |
| Cheetah Cat Limited | Administrative & support | 2022 |
| Chef Dreams Limited | Hospitality | 2025 |
| Chef Smith Catering Ltd | Hospitality | 2020 |
| Chef's Insta Food Ltd | Hospitality | 2024 |
| Chelmor Property Limited | Real estate | 1999 |
| Cheng XIN Trade Ltd | Wholesale & retail | 2019 |
| Chestnut Tree Limited | Administrative & support | 1980 |
| Childsplay Nursery LLP | | 2026 |
| China Garden PD Ltd | Hospitality | 2021 |
| China Kitchen (Felinfoel) Limited | Wholesale & retail | 2003 |
| Chiro Y CWM Ltd | Health & social care | 2025 |
| Chongololo Ltd | Manufacturing | 2024 |
| Chooselife Cymru | Health & social care | 2004 |
| Chris Townsend HR & Transformation Consulting Ltd | Administrative & support | 2025 |
| Chris Turrell Mortgages Ltd | Financial services | 2025 |
| Chrysalis Mind SET Coaching Ltd | Administrative & support | 2016 |
| Church Road Cardiff Limited | Construction | 2018 |
| Cilgwenyn BEE Farm CYF | Agriculture & fishing | 2019 |
| Cimla Properties Limited | Extraterritorial | 2014 |
| Cindar Limited | Professional & scientific | 2021 |
| City Roofing & Upvc Ltd | Construction | 2024 |
| CJ AGA Servicing Ltd | Construction | 2022 |
| CJD Carpentry Limited | Manufacturing | 2025 |
| Cjdpropertysolutions Limited | Real estate | 2025 |
| CJP Paraplanning Ltd | Financial services | 2013 |
| CK Top 10 Barber Ltd | Other services | 2025 |
| CL Property Management Ltd | Real estate | 2026 |
| CL Recruitment Ltd | Administrative & support | 2024 |
| Claire Thomas Photography Ltd | Professional & scientific | 2025 |
| Classic PVC (Holdings) Limited | Professional & scientific | 2014 |
| Classic PVC Conservatories Limited | Construction | 2014 |
| Classic PVC Limited | Wholesale & retail | 2007 |
| Clay Construction Limited | Construction | 2022 |
| Clean N Gleam (Commercial) Limited | Administrative & support | 2018 |
| Clean N Gleam (Domestic) Ltd | Administrative & support | 2022 |
| Cleanology South Wales Limited | Administrative & support | 2018 |
| Clear Conscience Counselling Ltd | Professional & scientific | 2020 |
| Clearshiftwellbeing Ltd | Information & communication | 2025 |
| Clickbox Ltd | Manufacturing | 2026 |
| Clinibus Ltd | Health & social care | 2022 |
| Cloham Limited | Wholesale & retail | 1965 |
| Clutterbuck Site Services Ltd | Construction | 2025 |
| Clyd Homes Limited | Construction | 2024 |
| CM Solar Surveys Limited | Professional & scientific | 2022 |
| CMC Electrical Solutions Limited | Construction | 2015 |
| Coach Glass Holdings Limited | Financial services | 2018 |
| Coach Glass Limited | Wholesale & retail | 1998 |
| Coach Wellbeing Initiative Ltd | Health & social care | 2025 |
| Coalbrook Surgery Limited | Health & social care | 2015 |
| Coast Asset Holdings Ltd | Real estate | 2022 |
| Coast Bathrooms and Kitchens Limited | Wholesale & retail | 2015 |
| Coast Electrical Contractors Limited | Administrative & support | 2017 |
| Coast Procurement Ltd | Professional & scientific | 2018 |
| Coastal Park Hotel Ltd | Hospitality | 2017 |
| Coco & Frida Ltd | Wholesale & retail | 2024 |
| Coco Bay Beach and Cafe Bar Ltd | Hospitality | 2023 |
| Coco Blush Boutique International Ltd | Wholesale & retail | 2019 |
| Coco's Wholesale Ltd | Wholesale & retail | 2017 |
| Coed Dinefwr Limited | Manufacturing | 2008 |
| Coedrath Park Management Company Limited | Real estate | 1974 |
| Coleg SIR GAR | Education | 2013 |
| Comcen Technology Ltd | Information & communication | 2006 |
| Commercial Flooring Contractors Ltd | Construction | 2018 |
| Commercial Marquee Hire Ltd | Other services | 2009 |
| Companion Technologies Ltd | Information & communication | 2026 |
| Comparemyoffice Limited | Extraterritorial | 2012 |
| Compliance Health & Safety Services Ltd | Education | 2016 |
| Compton & Family Limited | Professional & scientific | 2022 |
| Comserve (Wales) Ltd | Administrative & support | 2009 |