| Constellation Fleet Limited | Administrative & support | 2014 |
| Constituent Group Ltd | Wholesale & retail | 2020 |
| Construction Insure Ltd | Financial services | 2018 |
| Construction Invest Ltd | Hospitality | 2018 |
| Constructiva Holdings Limited | Financial services | 2025 |
| Constructiva Lettings Limited | Real estate | 2025 |
| Constructiva Limited | Construction | 2025 |
| Construx (UK) Limited | Construction | 1998 |
| Consultdin Ltd | Professional & scientific | 2026 |
| Consulting Services Ltd | Other services | 2018 |
| Container Safe Limited | Administrative & support | 2002 |
| Contemporary Interiors London Ltd | Construction | 2017 |
| Continuity Holdings Ltd | Wholesale & retail | 2022 |
| Contractors Legal GRP Limited | Administrative & support | 2009 |
| Controlequal Property Management Limited | Real estate | 1996 |
| Convene Construction Ltd | Construction | 2019 |
| Convertico Ltd | Professional & scientific | 2019 |
| Convexity Technologies Limited | Professional & scientific | 2025 |
| Conway Training Associates Ltd | Administrative & support | 2020 |
| Cookies London Ltd | Hospitality | 2016 |
| Cookpal Ltd | Education | 2025 |
| Cool Aircon Ltd. | Other services | 2011 |
| Cool Cats Club Limited | Other services | 2013 |
| Cool Hand Creative Limited | Real estate | 2005 |
| Coolac Ltd | Construction | 2024 |
| Cooper Coaching Ltd | Other services | 2025 |
| Coopers Investments Limited | Real estate | 1968 |
| Coops Consulting Ltd | Professional & scientific | 2019 |
| Copper 16 Ltd | Administrative & support | 2018 |
| Copper Beech Court (Whetstone) Management Company Limited | Households | 1988 |
| COR Logistics Ltd | Transport & logistics | 2019 |
| Coral Construction Ltd | Administrative & support | 2025 |
| Coralbells Care Services Ltd. | Administrative & support | 2015 |
| Cordell Marks Ltd | Other services | 2013 |
| Corders Farm Property Limited | Real estate | 2024 |
| Core Construction (Herts) Limited | Construction | 2014 |
| Corewell Services Ltd | Health & social care | 2026 |
| Corfig Limited | Administrative & support | 2009 |
| CORFU86 Ltd | Health & social care | 2022 |
| Corinthian Properties Limited | Real estate | 1983 |
| Cormallen Limited | Information & communication | 1999 |
| Cornerstone Employee Benefits Advisory Limited | Professional & scientific | 2026 |
| Cornerstone NG & UK Ltd | Wholesale & retail | 2019 |
| Cornishcoastal Ltd | Hospitality | 2026 |
| Corporate City Developments NO.2 Limited | Real estate | 2007 |
| Corporate Finance Research and Advisory Limited | Administrative & support | 2012 |
| Corporateregister.Com Limited | Professional & scientific | 1996 |
| Corprex Limited | Professional & scientific | 2022 |
| Corralea Limited | Professional & scientific | 2023 |
| Corsned Consulting Limited | Information & communication | 2005 |
| Cosio Construction Ltd | Construction | 2019 |
| Coskun Brothers Ltd | Financial services | 2026 |
| Cosmo House Limited | Real estate | 2009 |
| Cosmoblue UK Ltd. | Information & communication | 2024 |
| Cosmos Cakes Limited | Manufacturing | 2007 |
| Cosmos Twilight Limited | Real estate | 2022 |
| Cost Verification International Limited | Financial services | 2017 |
| Costa Driving School Limited | Education | 2024 |
| Costalex Limited | Hospitality | 2012 |
| Costas and Helen Ioannou LLP | | 2023 |
| Costef Limited | Financial services | 2025 |
| Costy Construction Ltd | Construction | 2020 |
| Cosy Home Trading Limited | Wholesale & retail | 2025 |
| Cota Construction (UK) Ltd | Construction | 2013 |
| Cotswold Gynaecology Limited | Health & social care | 2010 |
| Cotswold PUB Partnership Limited | Hospitality | 2022 |
| Cottisford Eight Ltd | Real estate | 1994 |
| Couinauds Research Ltd | Health & social care | 2022 |
| Coulwood UK Limited | Real estate | 2023 |
| Counselling Psychotherapy Oxford Ltd | Health & social care | 2013 |
| Count on (School Finance) Limited | Professional & scientific | 2010 |
| Country Courtyard Estates Limited | Construction | 2008 |
| Country House Weddings Holdings Ltd | Financial services | 2017 |
| Countrywide Developments (UK) Limited | Real estate | 2002 |
| Coup Medical Ltd | Administrative & support | 2013 |
| Courtmaster Properties Limited | Other services | 1995 |
| Covehall Limited | Real estate | 2005 |
| Coventry Central Investment Limited | Professional & scientific | 2013 |
| Coventry Land Investments Limited | Real estate | 2012 |
| Cowes Baryes Limited | Hospitality | 2018 |
| COX Format Developments Limited | Construction | 1994 |
| Cozy Draws Ltd | Arts & recreation | 2022 |
| Cozy LDN Ltd | Real estate | 2025 |
| Cpapa Limited | Real estate | 2018 |
| CPD Newco Limited | Real estate | 2016 |
| Cpfsportstherapy Ltd | Education | 2023 |
| CPS & Co Properties Ltd | Real estate | 2017 |
| CPS Secure Limited | Professional & scientific | 1999 |
| CPS Solutions Group Limited | Energy | 2020 |
| CR Tours Ltd | Transport & logistics | 2019 |
| CR5 Consulting Ltd | Administrative & support | 2025 |
| Craftship Limited | Information & communication | 2016 |
| Crafty Fellas London Ltd | Hospitality | 2013 |
| Craig Moffat Architects & Design Limited | Professional & scientific | 2002 |
| Cranford Consultancy Ltd | Wholesale & retail | 2025 |
| Cranford Properties Ltd | Real estate | 2025 |
| Cranover Properties Limited | Construction | 1966 |
| Crayborne Ltd | Professional & scientific | 2023 |
| Craymer Plumbing & Heating Ltd | Construction | 2019 |
| Cream Boutique Limited | Extraterritorial | 2013 |