| Carrington Oliver John Limited | Professional & scientific | 2018 |
| Carrington Property Ltd | Construction | 2019 |
| Carringtons Direct Limited | Wholesale & retail | 2022 |
| Carron Energy Holdings Limited | Professional & scientific | 2004 |
| Carron Energy Limited | Energy | 2009 |
| Carry Propertyholdings Ltd | Real estate | 2026 |
| Cars 4 Less Ltd | Transport & logistics | 2019 |
| Cars of Penarth Road Limited | Wholesale & retail | 2023 |
| Cars on Cars Ltd | Wholesale & retail | 2018 |
| Cars Pocket Watcher Ltd | Wholesale & retail | 2025 |
| Cars-Mrt Ltd | Transport & logistics | 2025 |
| Carsaledragons Limited | Wholesale & retail | 2024 |
| Carsnap Limited | Wholesale & retail | 2025 |
| Carston ETL Limited | Extraterritorial | 2024 |
| Carston Holdings Limited | Professional & scientific | 2001 |
| Cart Home UK Ltd | Wholesale & retail | 2022 |
| Carta & Wood Limited | Professional & scientific | 2025 |
| Cartaid Ltd | Manufacturing | 2025 |
| Carten 100 Limited | Arts & recreation | 2012 |
| Carter and Carter Developments Limited | Construction | 2017 |
| Carter Carmichael Limited | Professional & scientific | 2016 |
| Carter Developments (NE) Limited | Construction | 2016 |
| Carter Lauren (Leisure & Retail) Construction Limited | Professional & scientific | 2005 |
| Carter Lauren (Property) Limited | Financial services | 2012 |
| Carter Lauren Construction (Holdings) Limited | Extraterritorial | 2018 |
| Carter Lauren Construction Limited | Construction | 1993 |
| Carter Lettings and Property Management Ltd | Real estate | 2024 |
| Carter Professional Services Limited | Health & social care | 2022 |
| Carter Thomas Construction Ltd | Construction | 2016 |
| Carters Homes Ltd | Real estate | 2019 |
| Cartfusion Limited | Wholesale & retail | 2025 |
| Carthago Motor Company Ltd | Wholesale & retail | 2022 |
| Cartintek Ltd | Wholesale & retail | 2023 |
| Cartlidge & Stewart Limited | Health & social care | 2016 |
| Cartouche Quality Solutions Ltd | Professional & scientific | 2015 |
| Cartradeuk Ltd | Wholesale & retail | 2023 |
| Cartrans 3000. Ltd | Extraterritorial | 2018 |
| Cartref Limited | Health & social care | 2005 |
| Cartref Properties JT Ltd | Hospitality | 2025 |
| Cartref Properties LE Ltd | Real estate | 2025 |
| Cartrefi Bach Ltd | Real estate | 2021 |
| Cartrefi Cymru Co-Operative Limited | Health & social care | 1989 |
| Cartrefi GMB Limited | Real estate | 2023 |
| Cartvero Limited | Wholesale & retail | 2025 |
| Cartwheel Software Solutions Ltd | Information & communication | 2020 |
| Cartwright Construction (Cardiff) Limited | Construction | 2015 |
| Cartwright Construction Limited | | 1959 |
| Cartwright Travel Limited | Administrative & support | 2003 |
| Cartzen Group Limited | Wholesale & retail | 2026 |
| Caru Campers Ltd | Manufacturing | 2022 |
| Caru Music Ltd | Information & communication | 2019 |
| Carumbos | Professional & scientific | 2025 |
| Carus London Ltd | Real estate | 2019 |
| Carvajal Consultancy Limited | Information & communication | 2023 |
| Carvalho UK Trading Limited | Construction | 2020 |
| Carve Home Ltd | Manufacturing | 2024 |
| Carwhiff Ltd | Wholesale & retail | 2019 |
| Carwyn Jones Construction Limited | Construction | 2019 |
| Cary Technology Limited | Transport & logistics | 2024 |
| Carys Williams Camera Limited | Information & communication | 2022 |
| Carzai Ltd | Information & communication | 2023 |
| Carzon International Ltd | Wholesale & retail | 2019 |
| Carzone Warehouse Ltd | Wholesale & retail | 2010 |
| Carzoom Ltd | Financial services | 2019 |
| CAS Group Ltd | Administrative & support | 2017 |
| Casa Construct Ltd | Construction | 2023 |
| Casa Holdings Ltd | Construction | 2020 |
| Casa Rita Ltd | Hospitality | 2025 |
| Casa Tech Digital Ltd | Information & communication | 2025 |
| Casaba Trade Ltd | Wholesale & retail | 2025 |
| Casablanca Nights Ltd | Hospitality | 2023 |
| Casadella Limited | Wholesale & retail | 2025 |
| Casahub Limited | Information & communication | 2021 |
| Casahub Portfolio Ltd | Real estate | 2014 |
| Casatelecom Ltd | Information & communication | 2016 |
| Casaya Limited | Real estate | 2011 |
| Casc Properties Limited | Real estate | 2014 |
| Cascade Finance Limited | Financial services | 2006 |
| Cascade Industrial Ltd | Manufacturing | 2019 |
| Cascade Plumbing Solutions Ltd | Construction | 2025 |
| Cascadewm Ltd | Financial services | 2009 |
| Cascasa Ltd | Real estate | 2019 |
| Case Construction Advisory Ltd | Construction | 2019 |
| Case Consulting Solutions Ltd | Professional & scientific | 2026 |
| Case Entertainment Group Limited | Administrative & support | 2018 |
| Case Equipment Limited | Wholesale & retail | 2008 |
| Case Licenses Limited | Professional & scientific | 2016 |
| Case Morgan Developments Limited | Construction | 2017 |
| Case Properties Limited | Real estate | 2003 |
| Case Technology Ltd | Information & communication | 2012 |
| Casel Ltd | Wholesale & retail | 2025 |
| Casetone Corporation PC | | 2017 |
| Casevey Ltd | Manufacturing | 2025 |
| Casey Builders /Developers Ltd | Construction | 2018 |
| Casey Engineering Cymru Limited | Professional & scientific | 2014 |
| Cash Gear Limited | Information & communication | 2022 |
| Cash My Skills Limited | Administrative & support | 2021 |
| Cashbricks Limited | Administrative & support | 2022 |
| Cashflow Properties Ltd | Real estate | 2019 |
| Cashin Brothers Holdings Limited | Administrative & support | 2019 |