| Commando Fitness (UK) Limited | Other services | 2013 |
| Commercial Cleaning (SE) Ltd | Administrative & support | 2026 |
| Commercial Roofing & Cladding Ltd | Construction | 2024 |
| Commodity Search Partners Group Limited | Financial services | 2013 |
| Commodity Search Partners Limited | Administrative & support | 2008 |
| Commoditysp Limited | Administrative & support | 2015 |
| Commonside Capital Investments Limited | Financial services | 2025 |
| Community Financials Solutions Ltd | Extraterritorial | 2024 |
| Community Through Sound C.I.C. | Health & social care | 2025 |
| Compass Financial Consultants Limited | Financial services | 2010 |
| Compassionate Connections Ltd | Health & social care | 2022 |
| Compendium Wealth LLP | | 2020 |
| Compliance Building Control Ltd | Professional & scientific | 2019 |
| Computers for Charities | Administrative & support | 2005 |
| Computers for Charities Trading Ltd Ltd | Administrative & support | 2005 |
| Coney Brothers DRY Construction Limited | Construction | 1998 |
| Connaught House (Marine Parade) Limited | Real estate | 2020 |
| Connaught House (Marine Parade) Project Co Limited | Construction | 2026 |
| Connect Building Services Ltd | Construction | 2011 |
| Connect GRP UK Limited | Administrative & support | 2016 |
| Connect Recruitment Services Limited | Extraterritorial | 2020 |
| Connected Developments Limited | Construction | 2005 |
| Connecting Truths Ltd | Professional & scientific | 2019 |
| Connections Cafe Community Interest Company | Health & social care | 2024 |
| Conrad Bose Wealth Management Ltd | Professional & scientific | 2016 |
| Construct Sussex Ltd | Construction | 2022 |
| Consult UK Limited | Administrative & support | 2001 |
| Continua Coaching Limited | Professional & scientific | 2024 |
| Control Facilities Limited | Manufacturing | 1999 |
| Cool Tide Interactive Limited | Information & communication | 1999 |
| Coolconnections Limited | Arts & recreation | 2010 |
| Coolhandcoders Ltd | Information & communication | 2021 |
| Coomber Property Limited | Real estate | 2016 |
| Copaway Limited | Real estate | 2024 |
| Core Coaching Group International Ltd | Education | 2021 |
| Cormorant Limited | Real estate | 1994 |
| Cortlandt Property LLP | | 2008 |
| Corunum Consulting Ltd | Professional & scientific | 2019 |
| Cosmos Camping Limited | Hospitality | 2021 |
| Costcutter Hailsham Ltd | Wholesale & retail | 2011 |
| Cottonwood Interiors Limited | Manufacturing | 2014 |
| Country House Productions Limited | Information & communication | 2025 |
| Countrywide Care Network Limited | Other services | 1991 |
| County Medicare Professional Nursing & Care Services Limited | Health & social care | 2023 |
| County Office Supplies Limited | Wholesale & retail | 1988 |
| County Town Developments Limited | Construction | 2013 |
| Courtland Cars Limited | Wholesale & retail | 2012 |
| Cousin Construction Ltd | Professional & scientific | 2011 |
| Cowiretech Limited | Manufacturing | 2025 |
| CPS Supply Co Limited | Wholesale & retail | 1977 |
| Craft Time Limited | Wholesale & retail | 2013 |
| Crafted Electrical Ltd | Construction | 2024 |
| Craig James Financial Services Ltd | Financial services | 2019 |
| Crathorne Property Services Limited | Real estate | 2015 |
| Creative Curtains and Blinds (Sussex) Limited | Wholesale & retail | 2015 |
| Creative Testing Solutions Limited | Information & communication | 2025 |
| Cresco Developments LLP | | 2025 |
| Crestbell Limited | Health & social care | 2009 |
| Crick Electrical Solutions Limited | Construction | 2026 |
| Criptech Limited | Financial services | 2025 |
| Crocombe Building and Landscaping Limited | Administrative & support | 2021 |
| Cross in Hand Holdings Limited | Construction | 2024 |
| Crossday Productions Limited | Information & communication | 2002 |
| Crowhurst Builders Limited | Construction | 2013 |
| Crowhurst Developments Limited | Construction | 2016 |
| Crown Asphalt Limited | Construction | 2009 |
| Crown Wealth Limited | Administrative & support | 2009 |
| Croydon (Unique) Limited | Real estate | 1957 |
| CS Drainage Solutions Limited | Water & waste | 2019 |
| Csnel Ltd | Professional & scientific | 2023 |
| CT Automotive Repairs Limited | Wholesale & retail | 2024 |
| CTB Training Ltd | Education | 2014 |
| CTP Media Ltd | Professional & scientific | 2015 |
| Cube Estates Limited | Real estate | 2007 |
| Cudlipp Homes Ltd | Construction | 2017 |
| Cullimore Family LLP | | 2021 |
| Cupful of Kale Ltd | Other services | 2018 |
| Curtis Building Solutions Limited | Construction | 2015 |
| CWD Associates Limited | Professional & scientific | 2018 |
| CXO Nexus Europe Ltd | Information & communication | 2024 |
| Cyberscream Limited | Information & communication | 2008 |
| D a Theunissen Ltd | Health & social care | 2020 |
| D C M (South East) Limited | Administrative & support | 2004 |
| D J Mewett Limited | Administrative & support | 2003 |
| D K C Chui Ltd | Health & social care | 2017 |
| D M Landscapes and Groundworks Ltd | Construction | 2017 |
| D T Cleaning Limited | Administrative & support | 2019 |
| D&D Contracting Limited Liability Partnership | | 2024 |
| D&L House Clearances Ltd | Transport & logistics | 2015 |
| D&S Construction (SE) Ltd | Construction | 2015 |
| D.An.D. Joinery Ltd | Manufacturing | 1999 |
| D.B. Auto Repairs Limited | Wholesale & retail | 1991 |
| D4 Solutions Southern Ltd | Construction | 2026 |
| Dafrank Construction Ltd | Construction | 2022 |
| Dais Partnership LLP | | 2018 |
| Dale Saunders (Holdings) Ltd | Financial services | 2019 |
| Dale Saunders Investments Ltd | Real estate | 2022 |
| Dale Saunders Properties LLP | | 2022 |
| Dancia Limited | Wholesale & retail | 1997 |
| Dand Precast Concrete and Reconstructed Stone Limited | Manufacturing | 2006 |