| Cartrefi A&M Ltd | Construction | 2020 |
| Cartrefi Anna CYF | Real estate | 2025 |
| Cartrefi Croeso Cyfyngedig | Construction | 2018 |
| Casa MIA Swansea Limited | Hospitality | 2026 |
| Casey Industrial Services Limited | Construction | 2020 |
| Caspi Consulting Limited | Professional & scientific | 2023 |
| Cassar Finch Ltd | Real estate | 2020 |
| Castell Dwyrain Farms Ltd | Agriculture & fishing | 2002 |
| Castell Toch Caravan Site Limited | Hospitality | 2022 |
| Castle Ribs Ltd | Manufacturing | 2016 |
| Catalyst Carmarthenshire Ltd | Other services | 2020 |
| Catherine Simkiss Limited | Administrative & support | 2023 |
| CCS Property (Llandeilo) Limited | Real estate | 2018 |
| CDC Cymru Properties Ltd | Households | 2023 |
| Cdjd Holdings Ltd | Real estate | 2022 |
| Ceasar Carpentry & Construction Limited | Construction | 2024 |
| Ceesee Properties Ltd | Real estate | 2025 |
| Cegin Hedyn CIC | Hospitality | 2022 |
| Celtic Forge Ltd | Manufacturing | 2016 |
| Celtic Opticians Ltd | Wholesale & retail | 2017 |
| Celtic Podiatry (Carmarthen) Ltd | Health & social care | 2014 |
| Celtic Security Services Ltd | Administrative & support | 2020 |
| Centromark Organization PC | | 2017 |
| Centuri Ltd | Professional & scientific | 2026 |
| Centurion Risk Assessment Services Limited | Other services | 2016 |
| Cerebra - for Brain Injured Children and Young People | Administrative & support | 2001 |
| Cerecare Ltd | Health & social care | 2001 |
| Ceri Davies Planning Ltd | Professional & scientific | 2020 |
| Certa Cito Digital Ltd | Information & communication | 2025 |
| CFK Gym Ltd | Arts & recreation | 2019 |
| Chadzy`S Limited | Wholesale & retail | 2002 |
| Champaus Limited | Wholesale & retail | 2023 |
| Channex.Io Ltd | Information & communication | 2014 |
| Chaps (HPS) Wales Ltd | Construction | 2021 |
| Charades (Hereford) Limited | Hospitality | 2024 |
| Charles Carmarthen Limited | Professional & scientific | 2015 |
| Charles Morgan & Sons Limited | Agriculture & fishing | 2010 |
| Cheddar & District Funeral Directors Limited | Other services | 2014 |
| Chemodyn Ltd | Manufacturing | 2024 |
| Cherry Orchard Homes Limited | Real estate | 2004 |
| Chilly Drinks Limited | Wholesale & retail | 1997 |
| Choros.Io Limited | Information & communication | 2024 |
| Chris Cars Limited | Transport & logistics | 2003 |
| Chumroo Dermatology Care Ltd | Health & social care | 2024 |
| Church House Assets Ltd | Administrative & support | 2023 |
| Chygwyn Limited | Professional & scientific | 1999 |
| Cilevan Farm Limited | Agriculture & fishing | 2002 |
| Cinnamon Carmarthen Ltd | Hospitality | 2025 |
| Cirram Limited | Extraterritorial | 2002 |
| Cissonia Property Investments Limited | Professional & scientific | 2023 |
| City Developments (Swansea) Limited | Construction | 2005 |
| City One Limited | Real estate | 1999 |
| CJ Playground Services Ltd | Construction | 2019 |
| CJ Waste Limited | Water & waste | 2019 |
| CJW Aesthetics Limited | Other services | 2026 |
| CKL Ltd | Real estate | 2023 |
| Claremont Trade L.P. | | 2018 |
| Clarkes Farm Organics Ltd | Manufacturing | 2023 |
| Clawed & Dangerous Ltd | Other services | 2025 |
| Clay Shaw Butler Limited | Professional & scientific | 2008 |
| Clearbrook Farm Limited | Agriculture & fishing | 2023 |
| Clemclem Limited | Real estate | 2017 |
| Clews Estates Limited | Real estate | 2015 |
| Clews Homes Limited | Construction | 1998 |
| CLH Storage Limited | Real estate | 2021 |
| Cliff Jenkins Agri Services Limited | Manufacturing | 2013 |
| Clippertastic Dog Grooming Ltd | Other services | 2019 |
| Clive Jones Hydrographic Surveying Services Limited | Professional & scientific | 2009 |
| Cloke Holdings Ltd | Financial services | 2026 |
| Clos CWM Peris Properties Limited | Households | 2022 |
| Clos YR Odyn Limited | Households | 2022 |
| Club Cywion Cynwyl Ltd | Health & social care | 2024 |
| Clwb Caredig | Education | 2001 |
| Clwb Cynnwr CYF | Education | 1994 |
| Clwb Golff Caerfyrddin - Carmarthen Golf Club Ltd | Arts & recreation | 2023 |
| Clwb YR Enfys Limited | Education | 2023 |
| CN24P Ltd | Extraterritorial | 2016 |
| Coach House Butchery Ltd. | Wholesale & retail | 2023 |
| Coaching-Matters Ltd | Other services | 2026 |
| Coast to Coast Caravans Limited | Wholesale & retail | 2001 |
| Coast to Coast Leisure Parks Limited | Hospitality | 2025 |
| Cobwebs Limited | Wholesale & retail | 2008 |
| Coco Blush Boutique (Online) Ltd | Wholesale & retail | 2024 |
| Coco Nail Bar JD Ltd | Other services | 2025 |
| Coed Y Felin Ltd | Real estate | 2025 |
| Coffi Tilley Limited | Hospitality | 2025 |
| Coggswells Properties Ltd | Real estate | 2025 |
| Cogitech Limited | Information & communication | 2019 |
| Collecta Trade L.P. | | 2017 |
| Combidrive Limited | Other services | 1975 |
| Comfort Lifestyle Ltd | Wholesale & retail | 2020 |
| Completely Boring Limited | Information & communication | 2016 |
| Connect-Conserve Cymru / Cyswllt-Cadwraeth Cymru Community Interest Company | Arts & recreation | 2021 |
| Conrad Grindley LLP | | 2017 |
| Contempo Catering Ltd | Hospitality | 2019 |
| Continental Retail (Carmarthen) Ltd | Construction | 2023 |
| Cooltech Midlands Limited | Construction | 2023 |
| Cooper HEW Limited | Hospitality | 2018 |
| Copefield Construction Limited | Construction | 2009 |
| Copper Hospitality Limited | Hospitality | 2022 |