| Classic Interiors (London) Limited | Administrative & support | 2003 |
| Classic Travel of Loughton Limited | Administrative & support | 1984 |
| Classman Limited | Households | 1995 |
| Clayton Precision Services Limited | Real estate | 2020 |
| Clean Change Company Limited | Professional & scientific | 2000 |
| Cleanfully Yours Limited | Other services | 2007 |
| Cleaning-Maintenance Company Limited | Administrative & support | 2005 |
| Clear International Consulting Limited | Professional & scientific | 2003 |
| Clear Sky Developers Ltd | Real estate | 2022 |
| Clementina Support Services Limited | Other services | 2016 |
| Clementine Recruitment (London) Ltd | Administrative & support | 2023 |
| Clifford Gardens Limited | Households | 1999 |
| Clifford Packaging Holdings Limited | Financial services | 1980 |
| Clifton Road Hair & Beauty Limited | Other services | 2004 |
| Clifton Terrace Property Investments Limited | Construction | 2010 |
| Clingplan Limited | Construction | 1979 |
| Clint Whelan Creatives (CWC) Limited | Information & communication | 2014 |
| Clive Bradley Limited | Arts & recreation | 2007 |
| Clivesdale Management Company Limited | Households | 1986 |
| Clock Face Luxury Properties Limited | Real estate | 2016 |
| Clockwork Digital Limited | Arts & recreation | 2008 |
| Clockwork Pyramid Limited | Other services | 2000 |
| Cloud Consulting and Technology Association | Information & communication | 2021 |
| Cloudm Limited | Information & communication | 2023 |
| Cloverdale Properties Limited | Real estate | 1993 |
| Cloverleaf Accountancy Services Limited | Professional & scientific | 2003 |
| Clovity Limited | Information & communication | 2023 |
| Clucas Consultants LLP | | 2003 |
| CME Future Limited | Professional & scientific | 2001 |
| CMR Southharrow Ltd | Hospitality | 2014 |
| CNS Properties Limited | Real estate | 2005 |
| Coast Telecom Limited | Wholesale & retail | 1999 |
| Cochita Limited | Health & social care | 2010 |
| Coco Fashion Consultancy Ltd | Manufacturing | 2021 |
| Coffey Contractors Limited | Extraterritorial | 2004 |
| Coldinn Group Ltd | Real estate | 2017 |
| Coldinn Ltd | Transport & logistics | 2020 |
| Coldzilla Ltd | Construction | 2023 |
| Coles Green Joinery Limited | Wholesale & retail | 1931 |
| Colham Self Serve Limited | Wholesale & retail | 1999 |
| Colm. Stack | | 1998 |
| Colophon & Lavengro Print Limited | Manufacturing | 1994 |
| Colourful Events Limited | Education | 2010 |
| COM Pact International Limited | Wholesale & retail | 1977 |
| Combat (Windows & Doors) Limited | Professional & scientific | 1983 |
| Combat Double Glazing Limited | Construction | 1983 |
| Combined Locksmiths Ltd | Information & communication | 2002 |
| Comfortmark Limited | Administrative & support | 1987 |
| Comlan Limited | Manufacturing | 2004 |
| Commerce Networks Limited | Information & communication | 2007 |
| Compactwise Ltd | Real estate | 2001 |
| Complete Constructions and Electrics Ltd | Construction | 2021 |
| Compunet Systems Limited | Information & communication | 2000 |
| Computer Accounting Consultancy Limited | | 1983 |
| Computer Learning Centre Limited | Education | 2001 |
| Computer Technology Support Limited | Transport & logistics | 1992 |
| Computer Wizz Kids Limited | Information & communication | 1994 |
| Comset Limited | Information & communication | 1990 |
| Concern SRI Lanka Foundation Limited | Education | 2007 |
| Concise Couriers Limited | Transport & logistics | 2002 |
| Concord Security (Alarm) Systems Limited | Manufacturing | 1986 |
| Concrete Aqua Guard (UK) Ltd | Construction | 2018 |
| Confidental Surgeries Ltd | Health & social care | 2009 |
| Congress Company Secretarial Services Ltd | Extraterritorial | 1998 |
| Connectwell Limited | Professional & scientific | 2007 |
| Connolly Consulting Limited | Health & social care | 2016 |
| Connolly Plumbing Services Ltd | Construction | 2003 |
| Consonance Project Management Limited | Professional & scientific | 2005 |
| Consort Contractor Services Ltd | Construction | 2015 |
| Consortia Europe Limited | Construction | 2005 |
| Consortia Property Management Services Limited | Real estate | 2006 |
| Constructameal LLP | | 2004 |
| Constructed Contractors Limited | | 2002 |
| Construction Safety UK Limited | Professional & scientific | 2007 |
| Construction Workers Limited | Extraterritorial | 2004 |
| Consultancy 360 Limited | Information & communication | 2013 |
| Contact 365 Limited | Transport & logistics | 2010 |
| Continental Pictures Limited | Arts & recreation | 1987 |
| Controls Interface Limited | Manufacturing | 2004 |
| Controtex Limited | Information & communication | 1995 |
| Cool Consultancy Limited | Administrative & support | 2014 |
| Coolbex Ltd | Administrative & support | 2001 |
| Coombelake Limited | Professional & scientific | 2002 |
| Cooper's Sales and Letting Agents Limited | Construction | 1983 |
| Coos Market Ltd | Wholesale & retail | 2025 |
| Coranit (UK) Limited | Wholesale & retail | 1999 |
| Corbus Europe Limited | Information & communication | 2003 |
| Core Health Specialist Consulting Ltd | Administrative & support | 2023 |
| Corium London Ltd | Wholesale & retail | 2025 |
| Cornercork Ltd | Wholesale & retail | 2025 |
| Corporate Business Funding Ltd | Extraterritorial | 1993 |
| Corporate Golf Events Limited | Arts & recreation | 2006 |
| Corporate Positioning Services Limited | Professional & scientific | 1988 |
| Cosmetic Solutions Limited | Health & social care | 2003 |
| Cosmopolitan Fragrances & Cosmetics Ltd | Extraterritorial | 1986 |
| Cosmos Consultants Limited | Professional & scientific | 2002 |
| Cost Analysts and Consultants Limited | Administrative & support | 2007 |
| Cotmandene Limited | Real estate | 1998 |
| Counselling Initiatives | Health & social care | 1999 |
| Countercom Limited | Administrative & support | 2005 |