| Clever Comms Ltd | Information & communication | 2020 |
| Click and Conquer Consultancy Ltd | Information & communication | 2024 |
| Click Holdings Group Ltd | Financial services | 2023 |
| Click Partner Ltd | Other services | 2014 |
| Click Print Limited | Administrative & support | 2009 |
| Client Engager Online Limited | Information & communication | 2018 |
| Clientark Software Technologies Ltd | Transport & logistics | 2021 |
| Clinical Ultrasound Consulting Limited | Health & social care | 2013 |
| Clipinteriors Limited | Construction | 2009 |
| Cloud Flicker Solutions Ltd | Information & communication | 2018 |
| Cloudit Tech Ltd | Information & communication | 2018 |
| Cloudtek Consulting Ltd | Information & communication | 2018 |
| Clyro Accountancy & Consulting Services Limited | Professional & scientific | 2007 |
| CM Sporting Club Limited | Arts & recreation | 2022 |
| CMB Horizons Ltd | Professional & scientific | 2025 |
| CME UK (Holdings) Limited | Professional & scientific | 2007 |
| Cmjw Limited | Professional & scientific | 2020 |
| Cmoina Ltd | Manufacturing | 2024 |
| Cmsn Ltd | Real estate | 2011 |
| Cnelm | Education | 2013 |
| CNK Homes Limited | Real estate | 2022 |
| CNK Limited | Real estate | 2021 |
| Coach JC: Navigate Change With Confidence Limited | Professional & scientific | 2026 |
| Coachedbyhm Limited | Other services | 2025 |
| Coaching 4 Everyone Ltd | Professional & scientific | 2004 |
| Coastair Chartering Ltd | Transport & logistics | 2022 |
| Cobon Ltd | Real estate | 2021 |
| Coclare Limited | Information & communication | 2005 |
| Code Compliance Solutions Ltd | Professional & scientific | 2022 |
| Code Octopus Limited | Information & communication | 2016 |
| Coded Monks Ltd | Information & communication | 2025 |
| Codeflow Solutions Ltd | Information & communication | 2024 |
| Codelooks Ltd | Information & communication | 2011 |
| Codepixel Technologies Limited | Information & communication | 2010 |
| Coffee Affairs Limited | Hospitality | 2022 |
| Coffee CUP Holdings Limited | Financial services | 2022 |
| Coffee CUP Solutions Limited | Information & communication | 2014 |
| Coffee CUP Technical Limited | Information & communication | 2019 |
| Coffeology Limited | Hospitality | 2023 |
| Coherent Technology Solutions Ltd | Information & communication | 2010 |
| Colex (U.K.) Limited | | 1983 |
| Coloma Wealth Management LLP | | 2011 |
| Colonial Equipment Finance Ltd. | Financial services | 2008 |
| Colostomy UK | Other services | 2005 |
| Colour Blue Productions Ltd | Professional & scientific | 2026 |
| Colour Genie Ltd | Extraterritorial | 2013 |
| Colourblocks Productions Limited | Information & communication | 2025 |
| Comfort Zone Careers Ltd | Professional & scientific | 2026 |
| Comfortzone Property Limited | Real estate | 2023 |
| Commercexchange Ltd | Information & communication | 2006 |
| Commercial Nexus Ltd | Information & communication | 2024 |
| Community Golf and Leisure Trust | Health & social care | 2018 |
| Companion Care Solutions Limited | Administrative & support | 2019 |
| Compass Executive Cars (UK) Ltd | Transport & logistics | 2012 |
| Compass Executive Cars Berkshire Ltd | Transport & logistics | 2026 |
| Competera UK Limited | Information & communication | 2019 |
| Complaibridge Ltd | Information & communication | 2025 |
| Complete Bike Recovery Ltd | Other services | 2018 |
| Complete Optimisation Ltd | Information & communication | 2024 |
| Complian AI Ltd | Information & communication | 2026 |
| Composo Limited | Information & communication | 2023 |
| COMPUTEIT4U Limited | Other services | 2023 |
| Conan Biopharma Consulting Ltd | Professional & scientific | 2020 |
| Concept 2 Bespoke Limited | Construction | 2019 |
| Concept 2 Construction Limited | Construction | 2008 |
| Concept 2 Homes Ltd | Construction | 1971 |
| Concept GAS Fire Suppression Ltd | Manufacturing | 2023 |
| Concept Support Solutions Limited | Administrative & support | 2020 |
| Concoat Holdings Limited | Professional & scientific | 1969 |
| Concoat Limited | Professional & scientific | 2006 |
| Condimentz Ltd | Hospitality | 2021 |
| Confetti Crew Ltd | Hospitality | 2025 |
| Connect Social Technology Ltd | Information & communication | 2026 |
| Connectivity Experts Ltd | Information & communication | 2020 |
| Connectivity Ltd | Information & communication | 2013 |
| Connectivity Plus Limited | Information & communication | 2000 |
| Conrad Designer Bathrooms Limited | Extraterritorial | 2010 |
| Conscious Coaching and Consulting Ltd | Professional & scientific | 2023 |
| Construction Futures Limited | Administrative & support | 2018 |
| CONSULTANCY-66 Ltd | Information & communication | 2023 |
| Contact Seven Ltd | Information & communication | 2012 |
| Continuous Beauty Ltd | Other services | 2025 |
| Contract Trading Services Limited | Construction | 1997 |
| Contractor Marketplace Limited | Administrative & support | 2018 |
| Controlcare Limited | Construction | 1993 |
| Controls & Skills Authority Ltd | Other services | 1962 |
| Convenient Hire Limited | Administrative & support | 1992 |
| CONVERSE360 Limited | Information & communication | 2018 |
| Cooper's Hill Recreational Trust Limited | Arts & recreation | 1972 |
| Coopermosses Limited | Construction | 2025 |
| Coord Global IT Solutions Ltd. | Information & communication | 2012 |
| Copeland Automotive Limited | Extraterritorial | 2024 |
| Copper & Stone Plumbing Co. Ltd | Construction | 2025 |
| Copper Connexions Ltd | Construction | 2008 |
| Copy by Kathryn Ltd | Professional & scientific | 2021 |
| COR Tech Ltd | Information & communication | 2023 |
| Core Build Projects Limited | Other services | 2019 |
| Corellia Financial Services Limited | Financial services | 2017 |
| Corfields (UK) Limited | Administrative & support | 2006 |
| Corian Consultants Ltd | Professional & scientific | 2025 |