| Byrgwm CYF | Other services | 2023 |
| Byron's Butchers Ltd | Wholesale & retail | 2013 |
| Bytecraft Forge Ltd | Professional & scientific | 2025 |
| C & C Garden and Maintenance Services Limited | Administrative & support | 2025 |
| C and R Lettings Limited | Real estate | 2016 |
| C Davies Properties Ltd | Real estate | 2020 |
| C G Roberts Services Ltd | Administrative & support | 2019 |
| C M Davies Limited | Transport & logistics | 2017 |
| C P Aerials Limited | Information & communication | 2012 |
| C&D Service Holdings Ltd | Professional & scientific | 2025 |
| C&S Sutcliffe Ltd | Wholesale & retail | 2022 |
| C.A. Jones Limited | Agriculture & fishing | 2010 |
| C.K. Golder Limited | Transport & logistics | 2013 |
| C.R.S Recovery Ltd | Wholesale & retail | 2025 |
| Cabna Ltd | Professional & scientific | 2004 |
| CAE Developments Limited | Extraterritorial | 2010 |
| CAE Fynnon Management Company Limited | Households | 2007 |
| CAE Rosser Farm Developments Limited | Real estate | 2015 |
| Caeau Tafarn Newydd Ltd | Real estate | 2025 |
| Caer Construction Limited | Construction | 2019 |
| Caer Scaffolding Limited | Construction | 2020 |
| Cafe Fair Trade Limited | Wholesale & retail | 2010 |
| Caffi Castell Amroth Limited | Hospitality | 2026 |
| Caffi Traeth Limited | Hospitality | 2019 |
| Callglass Limited | Extraterritorial | 2000 |
| Calon WEN Dairy Produce Ltd | Manufacturing | 2002 |
| Calon WEN Organic Milk Co Operative Ltd | Wholesale & retail | 2000 |
| Calypso Engineering L.P. | | 2018 |
| Cambrian Investco Ltd | Financial services | 2021 |
| Cambrian Mental Health Law Ltd. | Professional & scientific | 2017 |
| Cambrian Property Services Ltd | Administrative & support | 2026 |
| Cannon Bridge Trinity ST David LLP | | 2015 |
| Canolfan Cymdeithasol Alma | Other services | 2002 |
| Canolfan Cymdeithasol Cynwyl Elfed | Other services | 2002 |
| Capable Staff Ltd | Administrative & support | 2017 |
| Capeclear Asset Management Limited | Extraterritorial | 2001 |
| Capel Solutions Limited | Information & communication | 2013 |
| Captain JAC Ltd | Information & communication | 2013 |
| Car Sales in Swansea Ltd | Wholesale & retail | 2022 |
| Car Shine Hand Car Wash Limited | Administrative & support | 2024 |
| Cardamom Ltd | Hospitality | 2025 |
| Cardiff Property Developments Ltd | Construction | 2024 |
| Cardsforeveryone.Co.Uk Ltd | Wholesale & retail | 2012 |
| Caretta Properties Ltd | Real estate | 2025 |
| Carhart Consultancy Limited | Hospitality | 2015 |
| Cariad Clean Ltd. | Administrative & support | 2024 |
| Cariad Pet Supplies Limited | Wholesale & retail | 2023 |
| Carl Rogers (Wales) Limited | Extraterritorial | 2003 |
| Carlsson Homes Ltd | Real estate | 2013 |
| Carmarthen (Express) Ltd | Wholesale & retail | 2021 |
| Carmarthen and District Autograss Club Limited | Arts & recreation | 1994 |
| Carmarthen and District Youth Opera | Arts & recreation | 1993 |
| Carmarthen and Pumsaint Farmers Limited | Real estate | 2013 |
| Carmarthen Antiques Centre P.C. | | 2013 |
| Carmarthen Asylum History Project Ltd | Arts & recreation | 2025 |
| Carmarthen Automotive Repair and Supplies Ltd | Wholesale & retail | 2014 |
| Carmarthen Camera Centre Limited | Wholesale & retail | 2000 |
| Carmarthen Care Clubs Ltd | Health & social care | 2009 |
| Carmarthen Community Leisure Ltd | Arts & recreation | 2022 |
| Carmarthen Deli Ltd | Wholesale & retail | 2023 |
| Carmarthen Demolitions Limited | Construction | 1991 |
| Carmarthen Dental Centre Ltd | Health & social care | 2020 |
| Carmarthen Developments Ltd | Construction | 2024 |
| Carmarthen Domestic Abuse Services Limited | Hospitality | 1997 |
| Carmarthen Funeral Director Limited | Other services | 2008 |
| Carmarthen GC Trading Ltd | Arts & recreation | 2016 |
| Carmarthen HAM Ltd | Manufacturing | 2003 |
| Carmarthen Lighting Centre Limited | Wholesale & retail | 2003 |
| Carmarthen Masonic Buildings Company Limited | Other services | 1911 |
| Carmarthen Motor Club Limited | Arts & recreation | 1989 |
| Carmarthen Property Services Limited | Manufacturing | 2024 |
| Carmarthen Refrigeration Limited | Construction | 2003 |
| Carmarthen Rugby Football Club Limited | Arts & recreation | 2012 |
| Carmarthen Rugs Ltd | Wholesale & retail | 2024 |
| Carmarthen Shopmobility Caerfyrddin | Other services | 2010 |
| Carmarthen Stall Limited | Wholesale & retail | 2003 |
| Carmarthen Town AFC Limited | Arts & recreation | 1999 |
| Carmarthen Town Football Club Limited | Arts & recreation | 1998 |
| Carmarthen Youth Project | Education | 2007 |
| Carmarthenshire Dairy Products Ltd | Manufacturing | 2018 |
| Carmarthenshire News Ltd | Information & communication | 2022 |
| Carmarthenshire People First | Other services | 2007 |
| Carmarthenshire Recycling & Environmental Services Limited | Water & waste | 1998 |
| Carmarthenshire Recycling Company Limited | Water & waste | 2000 |
| Carmarthenshire Recycling Research Centre Limited | Water & waste | 2001 |
| Carmdent Ltd | Health & social care | 2026 |
| Carms Property Rentals Limited | Hospitality | 2012 |
| Carningli Trust(The) | Health & social care | 1985 |
| Caron Renewables Ltd | Energy | 2015 |
| Carpedi Cartrefi Cynnes CYF | Wholesale & retail | 2021 |
| Carpenters B & B Limited | Hospitality | 2024 |
| Carpenters Broadway Limited | Hospitality | 2024 |
| Carreg YR Hebog Ltd | Real estate | 2025 |
| Carrom Ltd | Wholesale & retail | 2020 |
| Cartcom PC | | 2018 |
| Carter Diggers UK & NI Limited | Wholesale & retail | 2020 |
| Cartref CMJ Ltd | Real estate | 2021 |
| Cartref Designs Limited | Professional & scientific | 2007 |
| Cartref Hapus Limited | Financial services | 2022 |
| Cartrefi a Datblygiadau Sharp CYF. | Real estate | 2020 |