| Concrete Innovations Ltd | Manufacturing | 2018 |
| Conduiit Ltd | Extraterritorial | 2021 |
| Cone Donkey Labour Supply Ltd | Construction | 2018 |
| Conica Ltd | Manufacturing | 1990 |
| Consult Moore Limited | Professional & scientific | 2025 |
| Consultika (Collingham) Limited | Professional & scientific | 2016 |
| Consume IT Limited | Wholesale & retail | 2003 |
| Container Rack Limited | Wholesale & retail | 2015 |
| Contemporary Art Newark CIC | Wholesale & retail | 2023 |
| Convert Online Sales Limited | Wholesale & retail | 2025 |
| Cook House Holdings Limited | Financial services | 2021 |
| Cooks Appliance Centre Limited | Wholesale & retail | 2000 |
| Cooper Martin Ltd | Professional & scientific | 2020 |
| Coreline Services UK Ltd | Administrative & support | 2026 |
| Corral AI, Inc. | | 2026 |
| Corsaitalia Ltd | Wholesale & retail | 2026 |
| Cosgroves the Jewellers Limited | Wholesale & retail | 1979 |
| Cosmo Limited | Manufacturing | 1983 |
| Cosmoway Limited | Real estate | 2001 |
| Cosy Corner Agency Ltd | Information & communication | 2025 |
| COT Projects Ltd. | Energy | 2011 |
| Cotham Farms Limited | Agriculture & fishing | 1985 |
| Couldwell Property Solutions Ltd | Construction | 2021 |
| Country Kids Day Nursery Kneesall Limited | Education | 2018 |
| Countryfield (Village) Homes Limited | Construction | 1997 |
| Coupland Services Ltd | Information & communication | 2021 |
| Courtyard Trading Company Limited | Hospitality | 2019 |
| Covergold (N.C.V.) Limited | Information & communication | 2000 |
| Cowslip Solutions Ltd | Other services | 2010 |
| COX Catering Ltd | Hospitality | 2023 |
| COX Property Investing Limited | Real estate | 2018 |
| CP & PS Ltd | Administrative & support | 2011 |
| CP Elveden Village Limited | Real estate | 2011 |
| CP Longleat Village Limited | Real estate | 2011 |
| CP Mgmt Limited | Other services | 2011 |
| CP Sherwood Village Limited | Real estate | 2011 |
| CP Whinfell Village Limited | Real estate | 2011 |
| CP Woburn (Operating Company) Limited | Hospitality | 2011 |
| CPJ Energy Services Limited | Professional & scientific | 2023 |
| CPUK6 Holdco Limited | Financial services | 2020 |
| CPUK6 Limited | Financial services | 2020 |
| CR Beard Farmers Limited | Agriculture & fishing | 2006 |
| Crabtree Partnership Ltd | Hospitality | 2013 |
| Crawford Strategic Solutions Ltd | Professional & scientific | 2013 |
| CRE8 Studios Limited | Other services | 2015 |
| Creasey Consulting Limited | Professional & scientific | 2012 |
| Creation Science UK | Education | 2010 |
| Creative Conceptions Limited | Wholesale & retail | 2001 |
| Creative Retail Lighting Limited | Manufacturing | 2012 |
| Creative Space Properties Limited | Real estate | 2004 |
| Creatively Autistic Together CIC | Arts & recreation | 2025 |
| Crest Conversions Ltd | Manufacturing | 2025 |
| Crew & Co - Superyacht Crew Recruitment Ltd | Professional & scientific | 2026 |
| Crew Chain Ltd | Information & communication | 2025 |
| Crinnan Trading Limited | Agriculture & fishing | 2022 |
| Critical Industry Society Limited | Administrative & support | 2025 |
| Critical Infrastructure Protection Services Ltd | Public administration | 2012 |
| Crjrc Ltd | Administrative & support | 2015 |
| CRO Nest Ltd | Information & communication | 2025 |
| Cropton Brewery Limited | Wholesale & retail | 2025 |
| Cropton Brewery Properties Limited | Financial services | 2025 |
| Cropton Mill Estate Management Limited | Real estate | 2025 |
| Crosby Community Care Limited | Health & social care | 2024 |
| Crosse FIC Limited | Other services | 2021 |
| Croston 2020 Limited | Real estate | 2020 |
| Crow Park Farming Company | Agriculture & fishing | 2007 |
| Crown Farm MOT Station Limited | Wholesale & retail | 2003 |
| CRS GAS Solutions Limited | Construction | 2016 |
| Crss Electrical Ltd | Construction | 2026 |
| Cruise Ahead Limited | Administrative & support | 2004 |
| Crystal Vision a & B Ltd | Wholesale & retail | 2026 |
| Crystalline Cleaning Ltd | Administrative & support | 2023 |
| CSR Wire Industry Limited | Manufacturing | 2025 |
| CT Healthcare & EAR Services Ltd | Health & social care | 2019 |
| CT Solar Solutions Limited | Construction | 2026 |
| Ctag Limited | Other services | 2018 |
| CTD Defence Consultancy Ltd | Public administration | 2025 |
| CTD Tutoring Services Ltd | Education | 2026 |
| CTX Group Limited | Information & communication | 2023 |
| Ct’S Commercial Services Ltd | Administrative & support | 2024 |
| Cubedsix Ltd | Information & communication | 2015 |
| Culture & Engagement Experts Ltd | Professional & scientific | 2023 |
| Cumberland Place Management Company Limited | Households | 2003 |
| Cunliffe Management Limited | Real estate | 2025 |
| Cunx Sportswear Ltd | Manufacturing | 2017 |
| Cupit Plant Hire Limited | Administrative & support | 2008 |
| Curtain & Blind Design Ltd | Wholesale & retail | 2013 |
| Custom Creations Detailing Ltd | Wholesale & retail | 2014 |
| Custom Engineering Designs Ltd | Professional & scientific | 2017 |
| Custom Motorsport Fabrications Ltd | Manufacturing | 2018 |
| Customer Acquisition Limited | Professional & scientific | 2009 |
| Cvlinks Limited | Administrative & support | 2021 |
| Cvtn Services Limited | Health & social care | 2013 |
| CW Precision Limited | Construction | 2014 |
| CWM Roboras Ltd | Wholesale & retail | 2020 |
| CY Ice Blasting Limited | Administrative & support | 2024 |
| Cybernovae Ltd | Information & communication | 2018 |
| D & B Glazing Ltd | Construction | 2011 |
| D & B Steel Holdings Limited | Real estate | 2025 |
| D & B Steel Structures Ltd | Construction | 2019 |