| Cohesion Plus Kent | Arts & recreation | 2009 |
| COI Prints Ltd | Arts & recreation | 2022 |
| Coilee Limited | Wholesale & retail | 2025 |
| Coin Souvenir Ltd | Manufacturing | 2019 |
| Colchester PUB Co Ltd | Hospitality | 2026 |
| Coldpress Music Ltd | Information & communication | 2019 |
| Colenge Ltd | Professional & scientific | 2011 |
| Colin Ladd Associates Limited | Professional & scientific | 2004 |
| Colin Read Consulting Ltd | Extraterritorial | 2022 |
| Colina Management Limited | Arts & recreation | 2017 |
| Collabo Consulting Limited | Information & communication | 2020 |
| Collaborative Innovation Services Limited | Administrative & support | 2015 |
| Colleen Harney Management Services Limited | Professional & scientific | 2006 |
| Collinscooling Limited | Construction | 2026 |
| Colorcon European Holdings (NO.5) Limited | Financial services | 2012 |
| Colour Check Ltd | Construction | 2022 |
| Colour Tech (UK) Ltd | Wholesale & retail | 2003 |
| Columbia Flooring PLC | Wholesale & retail | 1970 |
| Combat Legal Costs Ltd | Professional & scientific | 2024 |
| Commara AI Ltd | Administrative & support | 2021 |
| Commflow Solutions UK Ltd | Construction | 2023 |
| Comos Construction Ltd | Construction | 2023 |
| Compaas Ltd | Manufacturing | 2019 |
| Compak Ramps Limited | Manufacturing | 2002 |
| Compass & Partners Ltd | Professional & scientific | 2023 |
| Complete Building Services Kent Limited | Construction | 2014 |
| Complete Construction Holding UK Ltd | Construction | 2023 |
| Complete Distribution and Logistics Limited | Professional & scientific | 2016 |
| Complete Drinks Ltd | Wholesale & retail | 2022 |
| Complete Equipment Hire Ltd | Administrative & support | 2025 |
| Complete Lift Solutions Limited | Construction | 2021 |
| Complete Logistics London Ltd | Transport & logistics | 2025 |
| Complete Management London Limited | Professional & scientific | 2025 |
| Complete New Cruse Ltd | Administrative & support | 2015 |
| Complete Recruitment Solutions Ltd | Administrative & support | 2024 |
| Complete Resourcing Solutions Limited | Administrative & support | 2021 |
| Complete Training Courses Ltd | Education | 2025 |
| Computer Eyes Limited | Extraterritorial | 2014 |
| Computer Visionary Systems Limited | Information & communication | 1997 |
| Comunitee House Ltd | Real estate | 2020 |
| Cona Solutions Limited | Health & social care | 2019 |
| Conceptualize Solutions Ltd | Information & communication | 2025 |
| Concrete Construction United Limited | Construction | 2000 |
| Concrete Construction Utilities Limited | Construction | 2004 |
| Concrete Cutting United Limited | Construction | 2011 |
| Concrete Rose Consulting Limited | Information & communication | 2019 |
| Confettiphotography Ltd | Professional & scientific | 2012 |
| Confidencecars Limited | Professional & scientific | 2024 |
| Coniston Dartford Limited | Professional & scientific | 2012 |
| Coniston FM Ltd | Construction | 2023 |
| Coniston Group Limited | Financial services | 2020 |
| Coniston Holdings Ltd | Financial services | 2024 |
| Coniston Hotel (Kent) LLP | | 2007 |
| Coniston Specialist Projects Limited | Construction | 2021 |
| Connect GAP Limited | Education | 2025 |
| Connect Link Solutions Ltd | Professional & scientific | 2026 |
| Connect Paving and Roofing Limited | Construction | 2023 |
| Connecting PD Limited | Information & communication | 2024 |
| Connectzone Consulting Ltd | Professional & scientific | 2021 |
| CONNEX3ION Ltd | Information & communication | 2013 |
| Conquer Leisure CIC | Arts & recreation | 2021 |
| Conradi Ltd | Extraterritorial | 2006 |
| Conradi Morrison & Co | | 2002 |
| Conscience Care Limited | Health & social care | 2020 |
| Consort Carpentry Limited | Construction | 2016 |
| Constant Fibreglass Limited | Manufacturing | 2011 |
| Constantia Homes Ltd | Real estate | 2024 |
| Constantia Property Investments Ltd | Real estate | 2024 |
| Constent Limited | Other services | 2025 |
| Construcion Consultancy Services Ltd | Professional & scientific | 2025 |
| Construct Scaffolding Services Limited | Construction | 2015 |
| Construction & Civils Ltd | Transport & logistics | 2020 |
| Construction Management Consulting Limited | Construction | 2007 |
| Construction Solutions Management Ltd | Construction | 2011 |
| Construction South Ltd | Construction | 2013 |
| Consultus (UK) Ltd | Real estate | 2005 |
| Consure Travels and Tours Ltd | Administrative & support | 2023 |
| Contemporary Back Office Solutions Limited | Information & communication | 2004 |
| Continent Electronics Ltd | Wholesale & retail | 2010 |
| Continental Cargo Carriers Ltd | Transport & logistics | 1988 |
| Control Group Cooperative Ltd | Other services | 2021 |
| Convery GMC Ltd | Transport & logistics | 2017 |
| Convoy Exports Ltd | Wholesale & retail | 2019 |
| Cooke Family Services Limited | Manufacturing | 2024 |
| Cool Dynamics Electrical Ltd | Construction | 2019 |
| Cool Dynamics Facilities Ltd | Energy | 2014 |
| Cool Dynamics Group Limited | Real estate | 2022 |
| Cool Dynamics Limited | Energy | 2008 |
| Cool Guys Air Conditioning Ltd | Construction | 2018 |
| Cool Hoop Ltd | Other services | 2024 |
| Cooling Matters | Other services | 2022 |
| Cooltech Services Ltd | Construction | 2015 |
| Coombs Electrical Limited | Construction | 2010 |
| Cooper & Sons Building & Maintenance Ltd | Construction | 2024 |
| Cooperman Constructions Ltd | Construction | 2024 |
| Coopers Estates Limited | Real estate | 2018 |
| Coopy Properties Ltd | Real estate | 2021 |
| Copia Group Ltd | Financial services | 2024 |
| Copia Metals London Ltd | Water & waste | 2019 |
| Copia Recycling Ltd | Water & waste | 2019 |