| Coracle Coaches Limited | Transport & logistics | 2011 |
| Cornerstones Cymru Limited | Real estate | 2008 |
| Corrfield Limited | Energy | 2014 |
| Cosmetic PR Limited | Professional & scientific | 2018 |
| Cougar (Chippenham) Limited | Construction | 2012 |
| Country Wise (Pendine) Limited | Administrative & support | 2007 |
| Cover Solutions (West Wales) Limited | Construction | 2023 |
| Cowindale Feeds Limited | Manufacturing | 2004 |
| Craddocks Light Haulage Limited | Transport & logistics | 2011 |
| Craig Davies Construction Ltd | Construction | 2018 |
| Craig Powell Limited | Construction | 2026 |
| Craig Taylor Ltd | Other services | 2016 |
| Cranc Cyclesport Limited | Wholesale & retail | 2013 |
| Creative Others Ltd | Wholesale & retail | 2021 |
| Cres (Wales) Limited | Extraterritorial | 2002 |
| Cres Energy Limited | Water & waste | 2015 |
| Cresselly Arms Ltd | Hospitality | 2011 |
| Criwdem Celf CIC | Arts & recreation | 2025 |
| Crm&S Roofing Services Ltd | Construction | 2023 |
| Croes Goch Farm Stores Limited | Wholesale & retail | 2001 |
| Croeso Cynnes Laugharne CIC | Health & social care | 2024 |
| Croeso Taxis Limited | Transport & logistics | 2018 |
| Crofty Properties Ltd | Real estate | 2016 |
| Crug Bach Limited | Real estate | 2020 |
| CRW Recycling Limited | Wholesale & retail | 2023 |
| Crystal Clear Technology Ltd | Information & communication | 2019 |
| CS Scaffolding and Safety Netting Services Limited | Construction | 2013 |
| CSH Solutions Limited | Professional & scientific | 2024 |
| CT Excavations Ltd | Administrative & support | 2022 |
| CTM Automotive Limited | Wholesale & retail | 2014 |
| Curious Web Ltd | Information & communication | 2019 |
| CWM Environmental Ltd. | Water & waste | 1991 |
| CWM TY Coed Ltd | Agriculture & fishing | 2023 |
| Cwmfit Limited | Arts & recreation | 2016 |
| Cwmni G R CYF | Agriculture & fishing | 2026 |
| Cwrt Malle Limited | Agriculture & fishing | 2004 |
| Cwrw Limited | Wholesale & retail | 2018 |
| Cwrw Studios CIC | Information & communication | 2024 |
| Cwtsh Hostel Ltd | Hospitality | 2020 |
| Cyber Confident Limited | Education | 2024 |
| Cyllid Cymru Finance Limited | Financial services | 2009 |
| Cymdeithas Gwasanaethau Gwirfoddol SIR GAR Carmarthenshire Association of Voluntary Services | Other services | 1997 |
| Cynnen Limited | Agriculture & fishing | 2019 |
| Cysgod Y Curyll Management Company Limited | Households | 2011 |
| D & T Group Ltd | Administrative & support | 2025 |
| D a Stoves Ltd | Construction | 2016 |
| D Clarke Pipe Welding & Fabrication Services Ltd | Manufacturing | 2026 |
| D H P Resources Limited | Transport & logistics | 2021 |
| D H R Rental Ltd | Households | 2025 |
| D Hywel Rees Ltd | Professional & scientific | 2014 |
| D M Kayes Holdings Limited | Construction | 2025 |
| D Melvyn Rees & SON Ltd | Wholesale & retail | 2013 |
| D W Evans Limited | Transport & logistics | 2012 |
| D W Sunrise Ltd | Health & social care | 2016 |
| D-12 Fitness Limited | Arts & recreation | 2011 |
| D.C Holdings (Carmarthen) Limited | Real estate | 2025 |
| D.Cox Building Contractors Limited | Construction | 2003 |
| D.S.W. Homes Ltd | Real estate | 2017 |
| D12 Gyms Ltd | Administrative & support | 2024 |
| DA Handbags Ltd | Wholesale & retail | 2023 |
| DAB (Cymru) Limited | Manufacturing | 2014 |
| Dabsa Limited | Real estate | 2021 |
| DAD & Sons Building Homes Ltd | Construction | 2020 |
| Daffodil Breaks Limited | Hospitality | 2018 |
| Dafydd Bowen Ltd | Health & social care | 2022 |
| Daichefuk Ltd | Hospitality | 2025 |
| Daiels Limited | Professional & scientific | 2022 |
| Dairy Active Ltd | Agriculture & fishing | 2014 |
| Dale Property Rentals Limited | Real estate | 2023 |
| Dalesdining Ltd | Hospitality | 2019 |
| Dalesspirits Ltd | Hospitality | 2020 |
| Dance Property Developments Limited | Real estate | 2026 |
| Danlyja Property Ltd | Real estate | 2026 |
| Dans Deliveries Ltd | Wholesale & retail | 2020 |
| Dare U2 Learn Ltd | Education | 2024 |
| Darren Davies Foot Trimming Ltd | Agriculture & fishing | 2010 |
| Datahound Limited | Information & communication | 2002 |
| Datrys Ltd | Professional & scientific | 2019 |
| Datrys Projects Ltd. | Administrative & support | 2024 |
| David Bourne Limited | Construction | 2024 |
| David L Thomas Limited | Professional & scientific | 2010 |
| Davies (Implements) Limited | Agriculture & fishing | 1958 |
| Davies Crane Hire Holdings Limited | Professional & scientific | 2014 |
| Davies Crane Hire Limited | Administrative & support | 1988 |
| Davies Crane Hire Plant Limited | Administrative & support | 2014 |
| Davies Crane Hire Property Ltd | Real estate | 2025 |
| Davies DA Properties Ltd | Real estate | 2026 |
| Davies Plant Hire Limited | Administrative & support | 2020 |
| Davies Property Developments Limited | Real estate | 2016 |
| Davies Rentals Limited | Real estate | 2023 |
| Davies Sound Limited | Information & communication | 2019 |
| Davis Ecom Ltd | Wholesale & retail | 2021 |
| Dayberg Projects PC | | 2018 |
| Daycrest Impex L.P. | | 2018 |
| Ddaear Ydym NI ! WE ARE Earth ! C.B.C. | Agriculture & fishing | 2021 |
| DDR Ventures Limited | Wholesale & retail | 2022 |
| Ddraig Aviation LLP | | 2025 |
| DE Rossi Griffiths Solicitors Ltd | Professional & scientific | 2022 |
| Dearden Cobbett Legal Ltd | Professional & scientific | 2025 |
| Debt and Credit Solutions Limited | Financial services | 2007 |