| Coombs Viaduct Ltd | Hospitality | 2017 |
| Cooper's Yard (Cardiff) Management Company Limited | Real estate | 1989 |
| Coopers Car Sales Ltd | Wholesale & retail | 2015 |
| Coopers Tyres Ltd | Wholesale & retail | 2023 |
| COP Services Limited | Administrative & support | 2025 |
| Copper Ice Ltd | Hospitality | 2024 |
| Copper Restaurant Group Limited | Hospitality | 2021 |
| Coracademy Limited | Information & communication | 2025 |
| Cornerstone Propertŷ Care Ltd | Administrative & support | 2026 |
| Corrin Ltd | Real estate | 2023 |
| Corrwg Ltd. | Real estate | 2020 |
| Cortexx Ltd | Education | 2022 |
| Cottam and Brookes Group Ltd | Financial services | 2026 |
| Countrywide Healthcare Supplies Holdings Limited | Wholesale & retail | 2013 |
| Countrywide Healthcare Supplies Limited | Wholesale & retail | 1996 |
| Cozee Property Group Ltd | Financial services | 2023 |
| CPE Productions Limited | Information & communication | 2021 |
| CPS (Wales) Group Limited | Financial services | 2010 |
| CPW Fire and Security Ltd | Administrative & support | 2024 |
| CR Precision Engineering Ltd | Professional & scientific | 2018 |
| Cracked Actors Salons Limited | Other services | 2014 |
| Craig Coombs Ltd | Real estate | 2025 |
| Crane & Plant World Limited | Administrative & support | 2018 |
| Cream Developments Ltd | Construction | 2024 |
| Create Caerphilly Skills and Wellbeing CIC | Arts & recreation | 2022 |
| Creative Collins Digital Marketing Limited | Professional & scientific | 2024 |
| Creative Property Centre Limited | Real estate | 2013 |
| Creative Touch Flooring Ltd | Construction | 2022 |
| Creazione 'in the Community' CIC | Education | 2019 |
| Creazione Dance Company Limited | Arts & recreation | 2009 |
| Creazione Ltd | Hospitality | 2019 |
| Crest Roofing and Building Limited | Construction | 2024 |
| Crest Roofing Products Ltd | Construction | 2025 |
| Crest Timber Frame Ltd | Manufacturing | 2025 |
| Crosshaven Properties Ltd. | Real estate | 2001 |
| Crossroads Educational Consultants Ltd | Education | 2023 |
| Crowley Developments Limited | Real estate | 2015 |
| CRT Building & Maintenance Limited | Construction | 2015 |
| Crucial Fitness Ltd | Arts & recreation | 2016 |
| CS - Promotions Limited | Manufacturing | 2010 |
| Csnj Ltd | Information & communication | 2024 |
| Ctrl Telecom Limited | Information & communication | 2017 |
| Culture Group Limited | Professional & scientific | 2003 |
| Curl Care Limited | Wholesale & retail | 2020 |
| Curtis Sumner Property Limited | Real estate | 2018 |
| Cutting Edge Welding Solutions Ltd | Manufacturing | 2025 |
| Cwac Cwac's Limited | Education | 2016 |
| Cwmni Tafarn Treftadaeth CYF | Hospitality | 2012 |
| Cwrt Griffin Management Company Ltd | Households | 2004 |
| Cwtch Comfort Caerphilly Limited | Wholesale & retail | 2018 |
| Cymorth Care Ltd | Health & social care | 2025 |
| Cymru Care (UK) Limited | Health & social care | 2009 |
| Cynefin Caerffili CIC | Administrative & support | 2024 |
| D & S Property Developments (Caerphilly) Limited | Manufacturing | 2016 |
| D & S Taxis Limited | Transport & logistics | 2015 |
| D R Powell Gardening, Building and Roofing Ltd | Construction | 2026 |
| D Sparks Transport Limited | Transport & logistics | 2016 |
| D&L Lodges Ltd | Hospitality | 2025 |
| D&S Decorating Solutions Ltd | Construction | 2025 |
| D&S Fabrications Ltd | Manufacturing | 2014 |
| D-Upgrades Limited | Wholesale & retail | 2016 |
| D. Evans and Sons Limited | Transport & logistics | 1961 |
| Dabberwolf Properties Limited | Real estate | 2023 |
| Dado Limited | Real estate | 2013 |
| DANW1276 Limited | Transport & logistics | 2026 |
| Daren Oliver Civil Engineering Services Limited | Professional & scientific | 2002 |
| Dark Element Brew Co Limited | Manufacturing | 2023 |
| Darkes & Lewis Ltd | Real estate | 2025 |
| Darllen Co Cyfyngedig | Education | 2021 |
| Darran Curtis Wealth Management Ltd | Professional & scientific | 2026 |
| Dartry Laundry Ltd | Other services | 2019 |
| Data Draig Ltd | Information & communication | 2024 |
| David Hoskins Enterprises Ltd | Wholesale & retail | 2018 |
| David Mahoney Productions Ltd. | Arts & recreation | 2014 |
| David Tomlins Construction Limited | Construction | 2008 |
| Dayworth Packaging Limited | Administrative & support | 2004 |
| Day’S Facilities Management Ltd | Administrative & support | 2018 |
| Day’S Services Ltd | Transport & logistics | 2026 |
| DBW Property Services Ltd | Construction | 2024 |
| DC Tax and Accounts Ltd | Professional & scientific | 2010 |
| DCF Motorcycle Parts Ltd | Wholesale & retail | 2025 |
| DD Automotive Ltd | Wholesale & retail | 2018 |
| Deacon Marriner LLP | | 2025 |
| Deb's Cottage Crafts Ltd | Manufacturing | 2021 |
| Declare Wills Limited | Administrative & support | 2019 |
| Decor Quip Limited | Wholesale & retail | 1999 |
| Deli Bakes Limited | Manufacturing | 2025 |
| Dell Designs Limited | Professional & scientific | 2010 |
| Delta Floors 23 Ltd | Construction | 2023 |
| Delta-Forse Electrical Ltd | Construction | 2026 |
| Dencraft Dental Laboratories Limited | Manufacturing | 2003 |
| Dersim Properties Ltd | Real estate | 2019 |
| Design Print Ltd | Manufacturing | 2023 |
| Destitute Clothing Ltd | Wholesale & retail | 2025 |
| Devil Nutrition Limited | Manufacturing | 2023 |
| Devonshire Pantry Ltd | Hospitality | 2026 |
| Dewin Ltd | Information & communication | 2013 |
| DFO Ltd | Wholesale & retail | 2025 |
| Dgwind Ltd | Professional & scientific | 2025 |
| DHG Bidco Ltd | Financial services | 2019 |