| Calon Properties Ltd | Households | 2023 |
| Cambrian (Tredegar) Limited | Hospitality | 2013 |
| Cambrian Care Consortium Limited | Health & social care | 2009 |
| Camtronics Limited | Manufacturing | 2003 |
| Camtronics Vale (Holding) Company Ltd | Professional & scientific | 2018 |
| Camu Ymlaen Support Services Limited | Administrative & support | 2008 |
| Capewell Consultants Limited | Professional & scientific | 2022 |
| Capital Valley Recycling Ltd | Water & waste | 2025 |
| Capital Valley Waste Management Ltd | Water & waste | 2025 |
| Cariad Coffee Limited | Wholesale & retail | 2026 |
| Carpenter Elite Logistics Limited | Transport & logistics | 2025 |
| Cartrefi Hapus Ltd | Real estate | 2023 |
| Carver & Beese Building Contractors Limited | Construction | 2014 |
| Castle Recovery & Storage Limited | Transport & logistics | 2019 |
| CDE Groundworks Limited | Construction | 2023 |
| CDM Heating Services Ltd | Construction | 2021 |
| CDR Solutions SW Ltd | Construction | 2023 |
| CDT Business Solutions Ltd | Information & communication | 2022 |
| Celtic Accountancy Services Ltd | Professional & scientific | 2022 |
| Celtic Cleans Limited | Administrative & support | 2026 |
| Celtic Heating & Plumbing Limited | Construction | 2013 |
| Central Fish Bar (Pontllotyn) Limited | Hospitality | 2023 |
| Central Surgery Nursing Home Limited | Health & social care | 2019 |
| Certicore Group Limited | Administrative & support | 2026 |
| CET HR Consultants Limited | Administrative & support | 2015 |
| Christian Phibben Limited | Construction | 2015 |
| Citizen Securities Limited | Professional & scientific | 2021 |
| CJB Theo Limited Ltd | Households | 2020 |
| Clark & Sons Flooring Ltd | Wholesale & retail | 2025 |
| Climapro Air Conditioning Ltd | Construction | 2026 |
| Cmkg Engineering Ltd | Professional & scientific | 2019 |
| CMM Distribution Ltd | Real estate | 2023 |
| Coast Function Ltd | Water & waste | 2024 |
| Codfather Tredegar Ltd | Hospitality | 2024 |
| Connor Edwards Carpentry Ltd | Construction | 2023 |
| Coolflow Airconditioning Limited | Construction | 2024 |
| Coopers Travel Ltd | Transport & logistics | 2024 |
| Copley Decor Limited | Professional & scientific | 2012 |
| Cotech Group Limited | Manufacturing | 2016 |
| Cotech Sensitising Limited | Manufacturing | 1979 |
| Coughlin Engineering Ltd | Construction | 2025 |
| Counselling Psychology UK Limited | Health & social care | 2005 |
| Cp.Mup. Ltd | Information & communication | 2023 |
| Creations of Cymru Film & Media Ltd | Administrative & support | 2016 |
| Creative GUN Engraving Ltd | Other services | 2026 |
| Creative Redevelopments Ltd | Real estate | 2023 |
| CRJ Property Management Ltd | Households | 2025 |
| Crown Commercial Properties Limited | Construction | 2021 |
| Crown Property Rentals & Services Limited | Real estate | 2023 |
| Crown RES Properties Limited | Real estate | 2021 |
| Crown Secure Self Storage Limited | Real estate | 2023 |
| CRW Financial Services Limited | Financial services | 2008 |
| Crystal Clear Financial Solutions Ltd | Financial services | 2013 |
| Crystal Windows (South Wales) Limited | Manufacturing | 2012 |
| Customer Services Solutions Ltd | Manufacturing | 2016 |
| CVR Group Limited | Financial services | 2026 |
| Cynnal Consulting Ltd | Professional & scientific | 2025 |
| D & C Property Management Limited | Real estate | 2015 |
| D & G Air Conditioning (Services) Ltd | Energy | 2015 |
| D&L Properties Tredegar Ltd | Hospitality | 2022 |
| D.F. Thatcher (Investments) Limited | Real estate | 1958 |
| Dagger Assets Ltd | Real estate | 2023 |
| Darcie & Rubie Properties Ltd | Real estate | 2025 |
| Darsons Building Services Ltd | Construction | 2021 |
| Deal Hub Ltd | Wholesale & retail | 2026 |
| Dean S Electrical Services Limited | Construction | 2017 |
| Deccan Creators Ltd | Wholesale & retail | 2025 |
| Derek's Xchange Ltd | Wholesale & retail | 2021 |
| Desirable Motors Ltd. | Wholesale & retail | 2013 |
| DH Andrews Services Limited | Other services | 2014 |
| Dhbi Limited | Information & communication | 2019 |
| Digital Antelope Limited | Information & communication | 2017 |
| Dirman Hand Car Wash Ltd | Wholesale & retail | 2025 |
| Discovery Glass UK Limited | Construction | 2017 |
| Divani Mail Order Limited | Extraterritorial | 1978 |
| Dizzy Kidz Tredegar Limited | Arts & recreation | 2018 |
| Djhp Ltd | Transport & logistics | 2022 |
| Dollmae Tiling Ltd | Construction | 2018 |
| Donkey Donuts Ltd | Manufacturing | 2019 |
| Doprops Ltd | Information & communication | 2014 |
| DP Dennehy & SON Electrical Contractors Limited | Construction | 2002 |
| DPS Contractors Limited | Construction | 2019 |
| Dragon Drascombe Limited | Administrative & support | 2017 |
| Dragon Recycling Solutions Ltd | Water & waste | 2006 |
| Draig Plastics and Homeware Ltd | Wholesale & retail | 2022 |
| DRS Plant Hire Limited | Administrative & support | 2023 |
| DRS Properties (SW) Limited | Construction | 2023 |
| DS & SRS Properties Ltd | Households | 2023 |
| Dukestown MOT Centre Limited | Wholesale & retail | 2016 |
| Dunkerton Utilities Limited | Construction | 2011 |
| D’Arcia Parfums Ltd | Wholesale & retail | 2025 |
| EC Property Management & Consultancy Ltd | Households | 2024 |
| Eco Heat Technology Ltd | Construction | 2019 |
| Eco Technology Ltd. | Water & waste | 1993 |
| Eco Technology Rhymney Limited | Manufacturing | 2025 |
| Eecj Brunning Ltd | Transport & logistics | 2025 |
| Eiddo Cariad CYF | Real estate | 2022 |
| EJA Consultancy Limited | Professional & scientific | 2011 |
| Element Solutions Ltd | Construction | 2020 |
| Elevated Elegance Pole & Aerial Ltd | Arts & recreation | 2025 |