| Classic Resin Driveways Ltd | Construction | 2022 |
| Classic Restoration Motorsport Ltd | Wholesale & retail | 2018 |
| Classic Stove Installations Ltd | Construction | 2014 |
| Classy Kitchen Ltd | Hospitality | 2024 |
| Clayson Bevan Properties Limited | Real estate | 2020 |
| CLC Estate Management Ltd | Real estate | 2018 |
| CLC Property Limited | Real estate | 2014 |
| Clean ME Clean Ltd | Construction | 2021 |
| Clean to the Core Ltd | Administrative & support | 2025 |
| Clean With a Gleam Ltd | Administrative & support | 2018 |
| Cleaner Carpets (Wales) Limited | Administrative & support | 2016 |
| Cleaning Masters Ltd | Real estate | 2022 |
| Clear AIM Consulting Ltd | Information & communication | 2016 |
| Clear EAR Health Ltd | Health & social care | 2024 |
| Clear Task AI Limited | Wholesale & retail | 2025 |
| Clearear by Holly Limited | Health & social care | 2023 |
| Clearsafe Partners Limited | Administrative & support | 2016 |
| Clearsafe Properties Limited | Real estate | 2023 |
| Clearview Independent Financial Advisers Limited | Financial services | 2004 |
| Clearway Property and Management Services Limited | Construction | 2023 |
| Clearway Property Services Limited | Construction | 2004 |
| Clement Medical Limited | Health & social care | 2023 |
| Clement Property Ventures Ltd | Real estate | 2024 |
| Clement Waste Management Limited | Water & waste | 2023 |
| Clements Jones Limited | Professional & scientific | 2005 |
| Clevedon Court Limited | Households | 1985 |
| CLH Trailers Ltd | Manufacturing | 2012 |
| Clickcartuk Limited | Wholesale & retail | 2025 |
| Clickmarine Ltd | Manufacturing | 2023 |
| Clifford Sewing Machines Ltd | Wholesale & retail | 2005 |
| Clifton Consultancy Ltd | Other services | 2023 |
| Clippers & Co (Wales) Limited | Other services | 2004 |
| Clippr Weather Protection Systems Limited | Manufacturing | 2021 |
| Cliste Limited | Information & communication | 2025 |
| Clive Howells Limited | Agriculture & fishing | 2022 |
| Clive Rees & Associates Ltd | Professional & scientific | 2016 |
| Clive.B.Williams Limited | Professional & scientific | 2010 |
| CLM Groundworks Limited | Construction | 2005 |
| CLM Property Rentals Limited | Real estate | 2012 |
| Clo&Flo Limited | Other services | 1993 |
| Clockhill Consultancy Limited | Professional & scientific | 2024 |
| Clockhill Properties Ltd | Households | 2021 |
| Clockwerk Limited | Construction | 2013 |
| Cloell Solutions Limited | Mining & quarrying | 2015 |
| Clonc Dental Limited | Health & social care | 2020 |
| Clos Salem Limited | Professional & scientific | 2016 |
| Clothes Clinic (Morriston) Limited | Other services | 2022 |
| Clothing UN Limited | Extraterritorial | 2013 |
| CLOUD9INE Communications Limited | Information & communication | 2018 |
| Cloudco Group Ltd | Professional & scientific | 2022 |
| Cloudinitium Ltd | Information & communication | 2020 |
| Cloverfields 28 Limited | Wholesale & retail | 2018 |
| CLR Properties Ltd | Real estate | 2025 |
| CLS Rentals Ltd | Real estate | 2024 |
| Club Class Executive Travel Europe Ltd | Transport & logistics | 2011 |
| Clubhill Limited | Real estate | 1979 |
| Clubhouse 1872 Ltd | Arts & recreation | 2025 |
| CLV Cargo and Logistics Group Limited | Transport & logistics | 2021 |
| Clwb Rygbi Ystradgynlais Bar Ltd | Hospitality | 2024 |
| Clwb Rygbi Ystradgynlais Ltd | Arts & recreation | 2017 |
| Clydach (Motors) Limited | Financial services | 1959 |
| Clydach BUS Company (Wales) Limited | Transport & logistics | 2026 |
| Clydach Business Centre Maintenance Services Ltd | Transport & logistics | 2026 |
| Clydach Community Gardens CIC | Arts & recreation | 2025 |
| Clydach Construction Limited | Construction | 1999 |
| Clydach Football Club CIC | Arts & recreation | 2025 |
| Clydach Hand Car Wash Ltd | Wholesale & retail | 2024 |
| Clydach Kebab CK Ltd | Hospitality | 2024 |
| Clydach Metals Limited | Wholesale & retail | 2025 |
| Clydach Self Storage Containers Limited | Transport & logistics | 2016 |
| Clydach Tavern Limited | Hospitality | 2020 |
| Clydfan Limited | Real estate | 2003 |
| Clyndu Land Ltd | Construction | 2026 |
| Clyne Estate Management Limited | Households | 2004 |
| Clyne Gardening Services Limited | Administrative & support | 2018 |
| Clyne Golf Club Limited | Arts & recreation | 1920 |
| Clyne Interior & Exterior Design Limited | Construction | 2006 |
| Clyne Property Enterprises Limited | Real estate | 1990 |
| Clyne Valley Community Project | Arts & recreation | 2011 |
| CM Renewable Energy Limited | Professional & scientific | 2025 |
| CM Residential Holdings Ltd | Real estate | 2025 |
| CM95 Limited | Financial services | 2021 |
| CME Accountancy Services Limited | Professional & scientific | 2013 |
| CMG Property Holdings Ltd | Real estate | 2018 |
| CMI (Wales) Limited | Hospitality | 2008 |
| CMJ Holdings Group Ltd | Real estate | 2025 |
| CML Jones Limited | Wholesale & retail | 2004 |
| CMP Carpentry Ltd | Construction | 2017 |
| CMR Property Group Limited | Real estate | 2025 |
| CMT Bricklaying Limited | Construction | 2017 |
| CNC Deliveries Limited | Transport & logistics | 2025 |
| CNG Holdings Limited | Financial services | 2022 |
| CNJ Carpentry Co Ltd | Construction | 2023 |
| CNS (Swansea) Limited | Mining & quarrying | 2009 |
| CNS Holdings Limited | Real estate | 2015 |
| Co Property Group Swansea Limited | Real estate | 2020 |
| Co.Hub 5.0 Ltd | Administrative & support | 2019 |
| CO2EFFICIENT Systems Limited | Professional & scientific | 2011 |
| Coach and BUS Association Cymru CYF | Other services | 2020 |
| Coakley Greene Limited | Wholesale & retail | 2022 |