| Celtic Staging Services Limited | Other services | 2024 |
| Celtic Vision Group Limited | Professional & scientific | 2004 |
| Celticfixer CYF | Arts & recreation | 2024 |
| Centre for Technology Economics | Professional & scientific | 2009 |
| Centriforce Limited | Manufacturing | 2013 |
| Cestrian Bars Ltd. | Hospitality | 2015 |
| CF5TRADING Ltd | Wholesale & retail | 2025 |
| CFM Fire & Security Ltd | Administrative & support | 2020 |
| CGI Windows & Doors Limited | Construction | 2019 |
| CH Fencing & Landscaping Limited | Administrative & support | 2023 |
| Chad Greenway Heating Ltd | Construction | 2023 |
| Change Your Country Ltd | Extraterritorial | 2016 |
| Chapter Digital Ltd | Information & communication | 2018 |
| Charcoal Crown Ltd | Hospitality | 2026 |
| Checkfire Ltd | Manufacturing | 2012 |
| Chedbrie Ltd | Construction | 2025 |
| Cheddie Consultancy Ltd | Information & communication | 2025 |
| Chemeng Limited | Professional & scientific | 2008 |
| Chilli Rail Limited | Construction | 2016 |
| Chips on the Rock Limited | Hospitality | 2025 |
| Choice 24/7 Limited | Manufacturing | 2013 |
| Choice Leisure Limited | Other services | 2017 |
| Chris Howell Timber & Landscape Supplies Limited | Wholesale & retail | 2005 |
| Chris Jackson Consulting Ltd | Professional & scientific | 2025 |
| Chris Nuttall Landscapes Ltd | Administrative & support | 2025 |
| Chris Page Landscapes Limited | Administrative & support | 2003 |
| Christopher David Willett Limited | Extraterritorial | 2024 |
| Christopher John Elliott Limited | Extraterritorial | 2022 |
| Christopher Joseph Limited | Professional & scientific | 2018 |
| Chunky 'S Chips Ltd | Hospitality | 2024 |
| Chunky CHIPS2 Ltd | Hospitality | 2024 |
| CIA Consulting Ltd | Financial services | 2019 |
| Cilk Road UK Ltd | Information & communication | 2025 |
| Circle in Square Ltd | Transport & logistics | 2015 |
| Citron Hygiene UK Limited | Water & waste | 1991 |
| City Space Development Ltd | Real estate | 2025 |
| City Vehicle Contracts Limited | Wholesale & retail | 2003 |
| CJ Mini Diggers Limited | Construction | 2013 |
| CJG Properties Ltd | Real estate | 2014 |
| CJS Global Ltd | Wholesale & retail | 2017 |
| Claire LEA Limited | Real estate | 2024 |
| Clarendon Construction Ltd | Construction | 2021 |
| Classly Ltd | Education | 2023 |
| Clay Construct Ltd | Construction | 2018 |
| CLC Smiles Ltd | Health & social care | 2025 |
| Cleaning Solutions 360 Ltd | Administrative & support | 2025 |
| Cleanwales Ltd. | Administrative & support | 2012 |
| Clear Minds Therapy C.I.C. | Education | 2023 |
| Clearchoice Windows Limited | Manufacturing | 2005 |
| Clearer Consultancy Limited | Administrative & support | 2015 |
| Clearpathuk Engineering Limited | Manufacturing | 2025 |
| Cleveland Biotech (Holdings) Limited | Financial services | 2013 |
| Cleveland Biotech Limited | Manufacturing | 1992 |
| Clic Creative Group Ltd | Professional & scientific | 2025 |
| Clik Quik Ltd | Professional & scientific | 2023 |
| CLM Safety Limited | Extraterritorial | 2009 |
| Cloudbound Systems Limited | Information & communication | 2023 |
| Clould IT Consulting Limited | Information & communication | 2023 |
| Cloverleaf Sales Ltd | Wholesale & retail | 2021 |
| Club Camelot Limited | | 1982 |
| Clutter Clear Ltd | Water & waste | 2024 |
| Clwb Marketing Limited | Administrative & support | 2026 |
| Clwb Ruperra Limited | Hospitality | 2024 |
| Clwb Y Ddraig CYF | Health & social care | 2019 |
| CMS IT Services Ltd | Information & communication | 2017 |
| Co-Operatives Wales Limited | Other services | 2005 |
| Coalshed Brewing Co Ltd | Manufacturing | 2021 |
| Coconailz Ltd | Other services | 2025 |
| Cods Corner (Caerphilly) Ltd | Hospitality | 2026 |
| Coed Llangwm Ltd | Real estate | 2017 |
| Coedcae Rosser Ltd | Agriculture & fishing | 2012 |
| Coedlas Limited | Construction | 2024 |
| Coffee for 2 Limited | Wholesale & retail | 2018 |
| Coffi a MWY Limited | Hospitality | 2026 |
| Coffi Hub Ltd | Hospitality | 2019 |
| Colin Robinson Printers Limited | Manufacturing | 1976 |
| Colshane Enterprises Ltd | Real estate | 2020 |
| Colwill Roofing Ltd | Construction | 2025 |
| Commercial Motors (UK) Limited | Wholesale & retail | 2004 |
| Community Music Wales/Cerddoriaeth Gymunedol Cymru | Education | 1992 |
| Complete Car Maintenance Limited | Wholesale & retail | 2023 |
| Complete Equestrian Ltd | Wholesale & retail | 2012 |
| Concept Document Solutions Limited | Manufacturing | 2012 |
| Concrete Barbers Ltd | Other services | 2025 |
| Connaught Compliance GAS Services Limited | Professional & scientific | 1995 |
| Connected Courier Services Limited | Transport & logistics | 2025 |
| Constrata UK Limited | Construction | 2009 |
| Constructaquote Limited | Financial services | 2006 |
| Construction Connect Limited | Construction | 2024 |
| Construction Drilling Services Ltd | Construction | 2019 |
| Consultative Sales & Strategy LLP | | 2023 |
| Contours and Curves Aesthetics Studio Ltd | Other services | 2024 |
| Contract Flooring Specialists Limited | Wholesale & retail | 1987 |
| Contracting CHS Ltd | Health & social care | 2024 |
| Contractorhub App Ltd | Construction | 2025 |
| Controlled Heating Solutions Ltd | Construction | 2011 |
| Conveyor Supplies & Maintenance Ltd | Manufacturing | 2020 |
| Conway Davis Limited | Professional & scientific | 2003 |
| Conwy Wills and Trusts Ltd | Professional & scientific | 2025 |
| Coombs Trading Limited | Wholesale & retail | 2023 |