| Coastal Awakening Ltd | Arts & recreation | 2025 |
| Coby Hung Limited | Professional & scientific | 2024 |
| Coed-Y-Lan Management Company Limited | Households | 2014 |
| COFFEE@64 Limited | Hospitality | 2024 |
| Coffi Co (Penarth) Ltd | Real estate | 2020 |
| Coffi Gallery Ltd | Hospitality | 2022 |
| Cofio Limited | Health & social care | 2010 |
| COG Accountancy Limited | Professional & scientific | 2008 |
| COG Entertainments Limited | Arts & recreation | 2018 |
| COG Office Solutions Limited | Professional & scientific | 2008 |
| COG School of Motoring Ltd | Other services | 2002 |
| Cohesive Logic Ltd | Information & communication | 2022 |
| Coincastle Property Management Limited | Households | 1984 |
| Colorpulse Ltd | Information & communication | 2024 |
| Columbus Forty Three Limited | Financial services | 2016 |
| Community Nursing Options Limited | Health & social care | 2005 |
| Companion District Ltd | Wholesale & retail | 2026 |
| Compass Penarth Ltd | Hospitality | 2015 |
| Compass Travel Management Limited | Administrative & support | 2020 |
| Competition Facilities Management Services Limited | Professional & scientific | 2012 |
| Computa-Centre Limited | Information & communication | 1998 |
| Concept Delta Limited | Information & communication | 2002 |
| Concrete Carrot Ltd | Manufacturing | 2013 |
| Concrete LAB Limited | Wholesale & retail | 2017 |
| Connect English Academy Ltd | Education | 2019 |
| Construction Footprint Ltd | Construction | 2012 |
| Construction Hub Recruitment Limited | Administrative & support | 2015 |
| Contigo Paraplanning Ltd | Administrative & support | 2024 |
| Core 3 Talent Ltd | Administrative & support | 2016 |
| Cosmeston Consultants Limited | Professional & scientific | 2013 |
| Cosy Cinema Cardiff Ltd | Hospitality | 2024 |
| Country Barks Ltd | Agriculture & fishing | 2026 |
| Cowbridge Building Company Limited | Wholesale & retail | 1983 |
| Cozwecan Ltd | Information & communication | 2025 |
| CP Asset Holdings Limited | Real estate | 2026 |
| CP Electrical & Renewables Ltd | Construction | 2025 |
| Cpos Trading Limited | Other services | 2016 |
| Cptsa Ltd | Information & communication | 2026 |
| Crackerjackpot Limited | Arts & recreation | 2012 |
| Cream Software Ltd | Administrative & support | 2017 |
| Created Looks Limited | Arts & recreation | 2016 |
| Creative Bridge Cardiff Ltd | Manufacturing | 2022 |
| Creative Casting Limited | Extraterritorial | 2021 |
| Creative Casting Services Limited | Extraterritorial | 2021 |
| Creative Talent Ltd | Extraterritorial | 2023 |
| Creditnet Limited | Professional & scientific | 2012 |
| Crispybirdpenarth Ltd | Hospitality | 2026 |
| Cromeuk Ltd | Hospitality | 2023 |
| Cross-Thomas Limited | Extraterritorial | 2017 |
| Crosswayz Limited | Real estate | 2002 |
| CTD Consult Limited | Professional & scientific | 2013 |
| CTQ Ventures Ltd | Real estate | 2020 |
| Cult Studios Ltd | Real estate | 2026 |
| Curo Advisers Limited | Financial services | 1993 |
| Curryleafpenarth Limited | Hospitality | 2023 |
| Cwrt Jubilee RTM Company Limited | Households | 2025 |
| Cyber Eats Ltd | Hospitality | 2020 |
| D Fofana Engineering Services Limited | Construction | 2015 |
| D Griffiths Financial Consulting Ltd | Professional & scientific | 2026 |
| D Harris Electrical Ltd | Construction | 2019 |
| D Logistics and Removals Limited | Transport & logistics | 2025 |
| D&D Investment Group UK Ltd | Real estate | 2025 |
| D.J. Shewring Limited | Health & social care | 2012 |
| Dailyspine Clinic Ltd | Administrative & support | 2009 |
| Daimat Ltd | Information & communication | 2021 |
| Dain-Smith Properties Limited | Real estate | 2018 |
| Damien Hatton Consulting Ltd | Information & communication | 2016 |
| Danatize Cleaning Services Ltd | Administrative & support | 2020 |
| Dark Origins Limited | Information & communication | 2003 |
| Darm Limited | Real estate | 2025 |
| Darren Jefferies Holdings Ltd | Financial services | 2025 |
| Darwin Accounting & Financial Services Ltd | Professional & scientific | 2024 |
| Data Delivery Network Limited | Information & communication | 2008 |
| Data Recovery Services Limited | Information & communication | 2002 |
| Davenhaven Limited | Real estate | 2025 |
| David James Technology Limited | Information & communication | 2008 |
| David Taylor Optical Limited | Health & social care | 2012 |
| David Wheeler Limited | Arts & recreation | 1986 |
| Dawn Health Clinic Ltd | Health & social care | 2022 |
| Day Community Housing Ltd | Real estate | 2017 |
| DAZ Colwill & SON Ltd | Manufacturing | 2014 |
| DB Industrial Ltd | Professional & scientific | 2021 |
| Deal Plant Limited | Wholesale & retail | 2021 |
| Dean and Sons Construction Ltd | Construction | 2021 |
| Debateamate Ltd | Manufacturing | 2026 |
| Deeper Marketing Ltd | Professional & scientific | 2021 |
| Delloyds Ltd | Administrative & support | 2015 |
| Derek Richards Limited | Other services | 2002 |
| DERIV8 Ltd | Health & social care | 2025 |
| Designer Websites Limited | Information & communication | 2006 |
| Designs on Life Limited | Education | 2007 |
| Dharma Risk Advisory Ltd | Information & communication | 2025 |
| Dharma Risk Ltd | Information & communication | 2025 |
| Digital Audience Data Limited | Professional & scientific | 2023 |
| Digital Marketing Advice Limited | Administrative & support | 2016 |
| Digital Places Limited | Extraterritorial | 2025 |
| Distinct Development Solutions Limited | Wholesale & retail | 2015 |
| Diva Foods Limited | Extraterritorial | 2010 |
| Diverse Design Interiors Limited | Construction | 2021 |
| DJ Properties (Wales) Limited | Real estate | 2007 |