| CDA Properties Limited | Real estate | 2014 |
| Cdaa Services Limited | Construction | 2023 |
| CDJ Ventures Group Ltd | Information & communication | 2023 |
| CDL Building and Carpentry Limited | Construction | 2013 |
| CDL Property Limited | Real estate | 2015 |
| Cdsm Holdings Limited | Information & communication | 2011 |
| Cdsm Interactive Solutions Ltd | Information & communication | 1999 |
| Cdsm International Solutions Ltd | Information & communication | 2021 |
| Cdso Limited | Wholesale & retail | 2012 |
| Cdtbsd Ltd | Professional & scientific | 2020 |
| CEC (Coyle Electrical Contractors) Ltd | Construction | 2002 |
| Cedar Tree House Limited | Real estate | 2018 |
| Cedarhale Limited | Health & social care | 2009 |
| Cedarwatch Ventures Limited | Financial services | 2025 |
| CEE Contractors Ltd | Construction | 2012 |
| CEE JAY Properties (CJP) Ltd | Real estate | 2023 |
| Ceetoo Architecture Limited | Professional & scientific | 2007 |
| Ceffyl Gwyn Ltd | Hospitality | 2022 |
| Cefn Hengoed Park | Arts & recreation | 2011 |
| Cefn Lodge Limited | Health & social care | 2016 |
| Ceir Phil Williams Cars Ltd | Wholesale & retail | 2015 |
| Celc Security Solutions Limited | Administrative & support | 2014 |
| Celebrations-Thailand Ltd | Administrative & support | 2025 |
| Celebrity Paper Masks Limited | Wholesale & retail | 2023 |
| Celmer Capital Ltd | Wholesale & retail | 2019 |
| Celtic Administration Services Ltd | Administrative & support | 2016 |
| Celtic and Oriental Ltd. | Real estate | 2017 |
| Celtic Automotive Limited | Wholesale & retail | 2009 |
| Celtic Caravan Care Ltd | Wholesale & retail | 2013 |
| Celtic Competitions Ltd | Arts & recreation | 2023 |
| Celtic Composites Ltd | Manufacturing | 2012 |
| Celtic Consultancy & Enterprises Limited | Professional & scientific | 2015 |
| Celtic Consultancy and Management Services Limited | Professional & scientific | 2018 |
| Celtic Consultancy Limited | Professional & scientific | 2013 |
| Celtic Deals Limited | Wholesale & retail | 2019 |
| Celtic Enterprises (Wales) Limited | Administrative & support | 2012 |
| Celtic Financial Services Limited | Financial services | 2001 |
| Celtic Flooring Ltd | Wholesale & retail | 2019 |
| Celtic Food and Drinks Limited | Hospitality | 2020 |
| Celtic Geophysics Limited | Professional & scientific | 2004 |
| Celtic Giftware Ltd | Wholesale & retail | 2018 |
| Celtic Green Gardens Limited | Administrative & support | 2025 |
| Celtic Health and Safety Limited | Professional & scientific | 2022 |
| Celtic Health Ltd | Public administration | 2020 |
| Celtic Healthcare Consultancy Ltd | Professional & scientific | 2023 |
| Celtic Herd Ltd | Agriculture & fishing | 2024 |
| Celtic International Freight Limited | Transport & logistics | 2020 |
| Celtic Minor Limited | Hospitality | 2014 |
| Celtic Mobility Limited | Wholesale & retail | 2023 |
| Celtic Mowers Limited | Wholesale & retail | 1977 |
| Celtic Office Cleaning Limited | Administrative & support | 2025 |
| Celtic PMC Ltd | Administrative & support | 2015 |
| Celtic Precision Ltd | Manufacturing | 2022 |
| Celtic Properties & Developments Ltd | Agriculture & fishing | 2016 |
| Celtic Properties 2 Limited | Real estate | 2017 |
| Celtic Properties One Ltd | Real estate | 2017 |
| Celtic Property Consulting Ltd | Real estate | 2015 |
| Celtic Property Management Limited | Real estate | 2014 |
| Celtic Publishing Ltd | Information & communication | 2000 |
| Celtic RAW Feeds Ltd | Wholesale & retail | 2020 |
| Celtic Star Kennels Ltd | Agriculture & fishing | 2020 |
| Celtic Strength & Fitness Ltd | Arts & recreation | 2020 |
| Celtic Tides Counselling Ltd | Education | 2022 |
| Celtic Valley Maintenance Ltd | Construction | 2026 |
| Celtic Vapours Trading Limited | Wholesale & retail | 2013 |
| Celtic Vascular Limited | Professional & scientific | 2023 |
| Celtic Wealth Management and Financial Planning Limited | Financial services | 2013 |
| Celtic Wildflowers Ltd | Agriculture & fishing | 2018 |
| Centano Limited | Manufacturing | 2015 |
| Center "I, YOU, WE" CIC | Real estate | 2022 |
| Centerline Construction Ltd | Construction | 2008 |
| Central Fleet Care Ltd | Wholesale & retail | 2021 |
| Centralshare Property Management Limited | Households | 1987 |
| Centre for Education and Community Ltd | Education | 2024 |
| Centre for Training and Education (Oxford) Ltd | Education | 2023 |
| Centurion (Parc Tawe I) Limited | Professional & scientific | 2005 |
| Centurion Quadrant Ltd | Real estate | 2024 |
| Centurion Tawe Ltd | Real estate | 2019 |
| Ceona Ltd | Hospitality | 2026 |
| CER Group Ltd | Construction | 2026 |
| Ceramiks Limited | Wholesale & retail | 1997 |
| Cerb Side Development Ltd | Real estate | 2023 |
| Ceri Hall Construction Ltd | Construction | 2009 |
| Ceri Lewis & Associates Limited | Real estate | 2007 |
| Ceri Thomas Ltd | Information & communication | 2023 |
| Cernunnos Landscaping & Property Maintenance CYF | Administrative & support | 2025 |
| Certa Technologies Limited | Information & communication | 2025 |
| Certia Education Ltd | Information & communication | 2026 |
| Certiflow Limited | Information & communication | 2025 |
| Certitec Limited | Information & communication | 2006 |
| Certitude Fire, Security & Electrical Ltd | Administrative & support | 2025 |
| CES Bristol Limited | Manufacturing | 1982 |
| CET (Swansea) Limited | Wholesale & retail | 2019 |
| Ceylon Bright FUN Holidays Ltd | Administrative & support | 2025 |
| CFA Ltd | Transport & logistics | 2016 |
| Cfcs Roofing Ltd | Construction | 2025 |
| CFH & PH Holdings Limited | Financial services | 2017 |
| CFN Enterprises Ltd | Real estate | 2022 |
| Cgharrison Developments Ltd | Real estate | 2023 |
| Cgharrison Properties Ltd | Real estate | 2023 |