| Concrete Canvas Technology Ltd. | Manufacturing | 2011 |
| Concrete Supplies Limited | Mining & quarrying | 2009 |
| Conklude Limited | Information & communication | 2009 |
| Connect Supply Limited | Information & communication | 2021 |
| Continuous Engagement Ltd | Professional & scientific | 2019 |
| Cord Investments (Cardiff) Limited | Hospitality | 1994 |
| Corehaus Group Ltd | Real estate | 2026 |
| Cossins Vehicle Movements Ltd | Transport & logistics | 2021 |
| Cosy Coffee Lounge Ltd | Hospitality | 2025 |
| County Tree Services Ltd | Administrative & support | 2023 |
| CR Rail Tech Limited | Construction | 2015 |
| Craddock Doors and Windows Ltd | Wholesale & retail | 2026 |
| Craftanize Ltd | Information & communication | 2018 |
| Craig Wallace Limited | Wholesale & retail | 2011 |
| Creative Holdings U.K. Ltd. | Wholesale & retail | 2023 |
| Creature Creations Ltd | Manufacturing | 2024 |
| Cross Inn Construction Consultants Ltd | Professional & scientific | 2023 |
| Crossways Projects Limited | Construction | 2023 |
| Crystal Clear Advisory Limited | Professional & scientific | 2015 |
| Crystal Wood Holdings Limited | Administrative & support | 2023 |
| CTC Autism Ltd | Other services | 2013 |
| Ctec Media Ltd | Professional & scientific | 2022 |
| Cuatro Motorsport Ltd | Wholesale & retail | 2021 |
| CUT Factory Limited | Manufacturing | 2021 |
| Cuttermans Coffee Limited | Hospitality | 2023 |
| Cuttimgrass & Co Cyfyngedig | Administrative & support | 2021 |
| Cyber-Cclab Ltd | Information & communication | 2010 |
| Cyfieithu Cardi CYF | Professional & scientific | 2016 |
| Cynefin Care Ltd | Health & social care | 2021 |
| D & a Naden Limited | Financial services | 2007 |
| D & L Housing & Rentals Ltd | Administrative & support | 2024 |
| D J Reynolds Builders Ltd | Construction | 2005 |
| D Lewis Consultants Ltd | Professional & scientific | 2023 |
| D P Foods Ltd | Hospitality | 2018 |
| D Rhys Edwards Ltd | Information & communication | 2014 |
| D S Construction 1 Limited | Construction | 2026 |
| D.C Building & Electrical Services Ltd | Administrative & support | 2015 |
| D.C Building Group Ltd | Real estate | 2023 |
| D.N.A. Business Support Services Limited | Professional & scientific | 2024 |
| DAI Software Limited | Information & communication | 2019 |
| Dai's Cabs Limited | Transport & logistics | 2014 |
| Dale Scorah Ltd | Transport & logistics | 2025 |
| Damp Logistics Ltd | Financial services | 2024 |
| DAN Display & Imaging Limited | Manufacturing | 2005 |
| Dark Green Media Limited | Information & communication | 2010 |
| Darp Limited | Real estate | 2022 |
| Darran Grant Ltd | Administrative & support | 2017 |
| Davelop Ltd | Professional & scientific | 2012 |
| David Copeland Limited | Information & communication | 2011 |
| David Davies Construction Management Ltd | Construction | 2018 |
| David Roberts Accountancy Services Ltd | Professional & scientific | 2013 |
| DB ENG Ltd | Professional & scientific | 2019 |
| DB Mech Ltd | Professional & scientific | 2022 |
| DB Property Management Ltd | Real estate | 2024 |
| DCR Inspection Systems Limited | Manufacturing | 2007 |
| DESIGN6061 Limited | Wholesale & retail | 2014 |
| Dhaliwal Properties Ltd | Real estate | 2010 |
| Dialoy Limited | Manufacturing | 1946 |
| Diamond Centre Wales Limited | Manufacturing | 2004 |
| Diana Brook Ltd | Arts & recreation | 2016 |
| Digidaydreamer Ltd | Wholesale & retail | 2023 |
| Direct Appointments Limited | Administrative & support | 2016 |
| Direct Kitchen Contracts Limited | Wholesale & retail | 2004 |
| Dirty Busters Ltd | Administrative & support | 2023 |
| Disturbance in the West Ltd | Administrative & support | 2025 |
| DJ Clark Consultancy Ltd | Professional & scientific | 2021 |
| DJA Consulting Ltd | Professional & scientific | 2026 |
| DJB (1) Ltd | Extraterritorial | 2026 |
| DJE Auto Electrics Ltd | Manufacturing | 2019 |
| DJE Property Holdings Limited | Financial services | 2015 |
| DJP (Wales) Ltd | Real estate | 2011 |
| DLM Structural Engineering Ltd | Manufacturing | 2026 |
| DMR QS & Estimating Services Ltd | Professional & scientific | 2021 |
| Dmts Catering Limited | Hospitality | 2016 |
| DO IT Your Own Way Ltd | Real estate | 2024 |
| Dom's Garage Ltd | Wholesale & retail | 2024 |
| Doomsday Print Co Limited | Manufacturing | 2024 |
| DOT Developments Ltd | Construction | 2012 |
| Doughzy Ltd | Hospitality | 2025 |
| Doyle Finance Limited | Financial services | 2003 |
| Dragon AI Consulting Ltd | Information & communication | 2026 |
| Dragon Fruit Holdings Limited | Real estate | 2016 |
| Dragon Location Services Limited | Professional & scientific | 2018 |
| Dragon Retail 326 Limited | Wholesale & retail | 2025 |
| Dragon Rose Properties Limited | Real estate | 2002 |
| Dragon Safety Ltd | Professional & scientific | 2015 |
| Dragon Ultrasound Ltd | Health & social care | 2021 |
| Draig Solutions Limited | Hospitality | 2015 |
| Dream Canvas Limited | Information & communication | 2006 |
| Dream Cleans by TD Ltd | Administrative & support | 2026 |
| Drrc Ltd | Hospitality | 2025 |
| DRS Mechanics Ltd | Professional & scientific | 2020 |
| DT Chem Ltd | Wholesale & retail | 2025 |
| Dtcs Financial Limited | Financial services | 2014 |
| Durbins Lettings Ltd | Real estate | 2015 |
| DV Engineering Management Ltd | Construction | 2024 |
| Dynamic Pool & Spas Limited | Water & waste | 2020 |
| D’Lites Limited | Hospitality | 2019 |
| E & E Property Developments Ltd | Real estate | 2019 |
| E J P Group Limited | Financial services | 2024 |