| Consulting ZEN Ltd | Professional & scientific | 2023 |
| Consultt AI Ltd | Information & communication | 2025 |
| Consysequip Holdings Limited | Professional & scientific | 1989 |
| Container Aerodynamics Ltd | Manufacturing | 2024 |
| Continuum Business Partnership Limited | Information & communication | 2022 |
| Contollo Solutions Limited | Administrative & support | 2018 |
| Contoured Comfort Limited | Manufacturing | 2016 |
| Control Panel Solutions Limited | Manufacturing | 2018 |
| Control Systems Management Limited | Professional & scientific | 2019 |
| Controlled Events Limited | Professional & scientific | 2011 |
| Convexia Limited | Professional & scientific | 2025 |
| CONVO247 Ltd | Professional & scientific | 2025 |
| Cookham Associates Limited | Professional & scientific | 2018 |
| Cookson Investment Holdings Limited | Real estate | 2025 |
| Cool Gardens Landscaping Limited | Administrative & support | 2003 |
| Cool Gardens Maintenance Limited | Administrative & support | 2010 |
| Cool Munchkin London Ltd | Manufacturing | 2014 |
| Cool Munchkin Ltd | Water & waste | 2014 |
| Coolstuff Ltd | Manufacturing | 2024 |
| Copal Properties Limited | Real estate | 2026 |
| Copia Catena Consulting Limited | Information & communication | 2012 |
| Copners Drive Management RTE Company Limited | Households | 2003 |
| Coppercat Solutions Ltd | Professional & scientific | 2010 |
| Coppergate Insurance Services Limited | Financial services | 1994 |
| Coppergate Management Limited | Professional & scientific | 2013 |
| Copperkins Lane Management Company Limited | Households | 2006 |
| Copton HIQ Ltd | Construction | 2020 |
| Copy Hallows Ltd | Information & communication | 2017 |
| Copyground Court Residents Association Limited | Administrative & support | 1989 |
| Corcorans Heating and Plumbing Ltd | Construction | 2025 |
| Core Fitness Ltd | Health & social care | 2017 |
| Core Health & Fitness Trading Limited | Wholesale & retail | 2000 |
| Core Infrastructure Limited | Professional & scientific | 2014 |
| Core Naturals Ltd | Manufacturing | 2025 |
| Core Project Management Ltd | Professional & scientific | 2026 |
| Corekids Physiotherapy Ltd | Health & social care | 2022 |
| Corentica Ltd | Information & communication | 2025 |
| Coretek Electronics Ltd | Manufacturing | 2025 |
| Coricraft Ltd | Construction | 2024 |
| Corihmar Limited | Real estate | 2024 |
| Corner Spice Grill Ltd | Hospitality | 2025 |
| Cornerstones Management Limited | Professional & scientific | 2010 |
| Cornish Fixings (Redruth) Limited | Wholesale & retail | 2011 |
| Coronation Road Limited | Real estate | 2005 |
| Corporate Events Limited | Extraterritorial | 2003 |
| Corporate Travel Solutions Ltd | Administrative & support | 2024 |
| Corpus Logic Ltd | Manufacturing | 2026 |
| Cosmetiqa Ltd | Wholesale & retail | 2018 |
| Cosmic Cloud Studios Ltd | Arts & recreation | 2024 |
| Cosmic Software Solutions Limited | Information & communication | 2024 |
| Cosmopolitan Internet Limited | Manufacturing | 1997 |
| Cosraf Limited | Real estate | 2018 |
| Costa Beijing Limited | Professional & scientific | 2007 |
| Costa China Holdings Limited | Professional & scientific | 1919 |
| Costa Express Holdings Limited | Professional & scientific | 2008 |
| Costa Express Limited | Administrative & support | 1996 |
| Costa International Limited | Professional & scientific | 1979 |
| Costa Limited | Manufacturing | 1976 |
| Costsaver Local Ltd | Wholesale & retail | 2019 |
| Cotswold View Residents Association Limited | Extraterritorial | 1999 |
| Cotswolds Digital Limited | Information & communication | 2023 |
| Coublis Limited | Information & communication | 2001 |
| Coulon Stone Limited | Construction | 1990 |
| Counter Strike Systems Limited | Information & communication | 2026 |
| Counterlabs Limited | Information & communication | 2026 |
| Country Cars (H.W.) Limited | Transport & logistics | 2014 |
| Country Clicks Event Hire Ltd | Professional & scientific | 2025 |
| Country Enterprises Limited | Wholesale & retail | 2017 |
| Country Lunchkins Ltd | Hospitality | 2019 |
| Countrylands RES. Assoc. (Penn) Limited | Real estate | 1994 |
| Countrywide Piano Centre Limited | Wholesale & retail | 1993 |
| County Motor Corporation Limited | | 1993 |
| Couple Koinonia | Other services | 2016 |
| Couriers App Limited | Transport & logistics | 2023 |
| Cournswood Group Limited | Professional & scientific | 2020 |
| Covalent International Ltd | Other services | 2023 |
| Covalent Systems Limited | Information & communication | 2018 |
| Covent Garden IP Ltd | Real estate | 2019 |
| Coworth Limited | Professional & scientific | 2011 |
| Coyle Consulting Ltd | Financial services | 2010 |
| Cozycorneruk Limited | Wholesale & retail | 2024 |
| CP Lomas Ltd | Professional & scientific | 2017 |
| CQ PA Services Limited | Administrative & support | 2025 |
| CQD Cleaning Services Ltd | Administrative & support | 2015 |
| CQD New GEN Ltd | Administrative & support | 2026 |
| Crabb and Templeton Associates Limited | Financial services | 1985 |
| Crabtree Techserv Ltd | Administrative & support | 2017 |
| Craig Ceiling Services Limited | Professional & scientific | 1980 |
| Cranborne Consulting Limited | Information & communication | 2013 |
| Cranbrook Immigration Ltd | Professional & scientific | 2024 |
| Cranford Consultants Limited | Real estate | 1988 |
| Cranwells Meadow Management Company Limited | Households | 2005 |
| Crawbridge Ltd | Professional & scientific | 2026 |
| Crctel Ltd | Information & communication | 2013 |
| Cre-Ayt Ltd | Manufacturing | 2026 |
| Crease Communications Limited | Information & communication | 2002 |
| Create Garden Rooms Ltd | Construction | 2021 |
| Creative Digital Marketing Agency Limited | Professional & scientific | 2024 |
| Creative Energy Ltd | Construction | 2020 |
| Creative Food Company Ltd | Hospitality | 2026 |