| Conrash Services Ltd | Information & communication | 2017 |
| Conroy Media Limited | Information & communication | 2003 |
| Conroy Paving & Driveways Ltd | Administrative & support | 2026 |
| Consaul Ltd | Construction | 2011 |
| Conscience Sincerit Ltd | Wholesale & retail | 2023 |
| Conscious Place Consulting Limited | Professional & scientific | 2016 |
| Consensys Health, Ltd | Information & communication | 2020 |
| Consept Shop Ltd | Wholesale & retail | 2020 |
| Consero Properties Ltd | Real estate | 2017 |
| Conservatory Base Company Ltd | Construction | 2010 |
| Consilio Construction and Architecture Ltd | Construction | 2020 |
| Consilium Consulting (Cardiff) Limited | Professional & scientific | 2014 |
| Consilium Consulting Group Limited | Professional & scientific | 2024 |
| Consilium Finance Limited | Financial services | 2023 |
| Consilium Investments LP | | 2022 |
| Consol Business PC | | 2014 |
| Console Empire Ltd | Wholesale & retail | 2025 |
| Consolidated Manufacturing Corporation Limited | Manufacturing | 1989 |
| Consolidated Power Tools Limited | Wholesale & retail | 1995 |
| Consono Ltd | Professional & scientific | 2019 |
| Consort Gardens Property Ltd | Real estate | 2019 |
| Consortiq US Ltd | Education | 2016 |
| Consortium X Ltd | Professional & scientific | 2022 |
| Constance Health & Social Care Limited | Health & social care | 2020 |
| Constance Wallace Ltd | Hospitality | 2017 |
| Constant Contracts Ltd | Administrative & support | 2016 |
| Constant Safety Limited | Professional & scientific | 2020 |
| Constantin Alpha Invest Limited | Administrative & support | 2015 |
| Constantin Beta Invest Limited | Administrative & support | 2015 |
| Constantine Roofing Services Ltd | Construction | 2025 |
| Consteel Ltd | Construction | 2020 |
| Construct Globally Limited | Wholesale & retail | 2023 |
| Constructa Building & Property Development Ltd | Construction | 2016 |
| Construction Compliance Services Ltd | Professional & scientific | 2018 |
| Construction Daily Limited | Construction | 2025 |
| Construction Experts Limited | Construction | 2017 |
| Construction Growth Partners Ltd | Other services | 2024 |
| Construction L&J Limited | Construction | 2019 |
| Construction Liviu 110 Limited | Construction | 2023 |
| Construction Management Services Limited | Construction | 2002 |
| Construction PAY Ltd | Information & communication | 2025 |
| Construction Payment Scheme Limited | Professional & scientific | 2021 |
| Construction Production Limited | Construction | 2022 |
| Construction Rentals East Ltd | Administrative & support | 2025 |
| Construction Staff 4 Ltd | Construction | 2015 |
| Construction Supply Limited | Construction | 2021 |
| CONSTRUCTION2DAY Ltd | Manufacturing | 2019 |
| Constructionandelectrical Limited | Construction | 2025 |
| Constructive Building Ltd | Information & communication | 2023 |
| Constructive Edge Consulting (EA) Ltd | Administrative & support | 2025 |
| Constructmypay Limited | Professional & scientific | 2025 |
| Consulenti Italiani Law International Limited | Professional & scientific | 2018 |
| Consult Capital (Fire) LLP | | 2008 |
| Consult Resolute Ltd | Information & communication | 2009 |
| Consultance Limited | Information & communication | 2025 |
| Consultancy Occupational Therapy Ltd | Professional & scientific | 2026 |
| Consultancy Services (South Wales) Ltd | Professional & scientific | 2025 |
| Consultancy TU Limited | Wholesale & retail | 2018 |
| Consultant CMO Ltd | Professional & scientific | 2022 |
| Consultant Field Engineering Ltd | Construction | 2013 |
| Consultant Lawyer Solutions Ltd | Professional & scientific | 2012 |
| Consulting & Trading Ltd | Wholesale & retail | 2020 |
| Consulting 2000 Project Services Limited | Professional & scientific | 2015 |
| Consulting Activities Ltd | Financial services | 2022 |
| Consumer Compensation Bureau Ltd | Financial services | 2013 |
| Consumer Credit Justice Limited | Financial services | 2009 |
| Consumer Distribution Ltd | Wholesale & retail | 2023 |
| Contact CBD Ltd | Other services | 2019 |
| Contact Centre Network(Ni) Ltd | Administrative & support | 2018 |
| Contacttree Dstr Ltd. | Information & communication | 2023 |
| Containanddrain Ltd | Construction | 2019 |
| Container City Cardiff Limited | Real estate | 2016 |
| Containercare (Southern) Limited | | 1936 |
| Contego Solutions Limited | Extraterritorial | 2018 |
| Contemporary Developments Ltd. | Construction | 2011 |
| Content Creators Resources Network Ltd | Professional & scientific | 2026 |
| Content Revamp Ltd | Information & communication | 2025 |
| Contessa Dolls Limited | Extraterritorial | 2021 |
| Conteu Ltd | Information & communication | 2024 |
| Contextuai Ltd | Information & communication | 2025 |
| Continental Advisors Ltd | Information & communication | 2019 |
| Continental Bazaar Cardiff Limited | Wholesale & retail | 2021 |
| Continental Equity 2022 Limited | Real estate | 2022 |
| Continental Haven Limited | Hospitality | 2025 |
| Continental Meat Products Limited | Wholesale & retail | 2003 |
| Continental Tiger Ltd | Wholesale & retail | 2023 |
| Continuum Blue Limited | Manufacturing | 2004 |
| Contour Fajas Limited | Manufacturing | 2016 |
| Contour Skin Ltd | Wholesale & retail | 2025 |
| Contra Inc | Information & communication | 2020 |
| Contract Consulting Ltd | Administrative & support | 2017 |
| Contract Leasing Limited | Wholesale & retail | 1986 |
| Contract Services Division Limited | | 1937 |
| Contractor & Schwarz Ltd | Health & social care | 2023 |
| Contractor Paye Limited | Administrative & support | 2018 |
| Contractor PSL Limited | Administrative & support | 2014 |
| Contractors 4 ALL Ltd | Construction | 2016 |
| Contractors R US Ltd | Real estate | 2018 |
| Contractr Ltd | Information & communication | 2021 |
| Contrain Ltd | Education | 2015 |