| Cardea 14 (Stanground) Residents Management Company Limited | Households | 2018 |
| Cardea 3D Enterprise (Stanground) Residents Management Company Limited | Households | 2016 |
| Cardinal Healthcare Group Ltd | Financial services | 2024 |
| Cardinal Healthcare Properties (East Anglia) Ltd | Real estate | 2022 |
| Cardinal Healthcare Properties Limited | Construction | 2014 |
| Cardinal Healthcare Property Development Ltd | Construction | 2024 |
| Cardinalis Developments Limited | Construction | 2001 |
| Cardinalis Holdings Limited | Financial services | 2021 |
| Cardinals Gate Flats Limited | Real estate | 1996 |
| Cardio Health Ltd | Health & social care | 2021 |
| Cardrona Drinks Company Ltd | Wholesale & retail | 2024 |
| Care AI Solutions Limited | Health & social care | 2024 |
| Care Angels 24/7 Limited | Health & social care | 2011 |
| Care Express International Ltd | Health & social care | 2023 |
| Care for Trees Limited | Administrative & support | 2011 |
| Care Investments Limited | Construction | 2026 |
| Care Link Homecare Ltd | Health & social care | 2025 |
| Care Network Cambridgeshire | Health & social care | 2007 |
| Care Profession Ltd | Health & social care | 2013 |
| Career Galaxee Limited | Administrative & support | 2022 |
| Careers Research and Advisory Centre (Crac) Limited(The) | Education | 1964 |
| Caregood Group Ltd | Wholesale & retail | 2020 |
| Careless Torque Limited | Professional & scientific | 2022 |
| CAREUK247 Fenland Ltd | Health & social care | 2021 |
| CAREUK247 Home Care Ltd | Health & social care | 2018 |
| CAREUK247 Ltd | Health & social care | 2015 |
| Carforyou Limited | Other services | 2015 |
| Cargo Restowe Devan Ltd | Transport & logistics | 2025 |
| Caring IZ Sharing Ltd | Other services | 2017 |
| Carl COX Fireplace Installations Limited | Construction | 2009 |
| Carl Dunn Building & Roofing Ltd | Construction | 2016 |
| Carl Zeiss Ltd | Professional & scientific | 1954 |
| Carlisle 79 Trustee Company 1 Limited | Professional & scientific | 2025 |
| Carlisle 79 Trustee Company 2 Limited | Professional & scientific | 2025 |
| Carlo Dichello Property Services Limited | Construction | 2014 |
| Carlo's Ices Limited | Wholesale & retail | 2018 |
| Carlogtech Solutions Ltd | Information & communication | 2025 |
| Carltonarms Limited | Hospitality | 2024 |
| Carmatech Ltd | Wholesale & retail | 2018 |
| Carmel Consulting Limited | Professional & scientific | 2017 |
| Carmelo (Cambridge) Limited | Other services | 2012 |
| Carmen's Pizzas Ltd | Hospitality | 2026 |
| Caroline Angel Ltd | Professional & scientific | 2011 |
| Caroline Cares for YOU Ltd | Health & social care | 2014 |
| Carolos Ltd | Wholesale & retail | 2023 |
| Carpe Diem Capital Limited | Real estate | 2024 |
| Carpetstobuy Ltd | Wholesale & retail | 2025 |
| Carra Consulting Ltd | Professional & scientific | 2026 |
| Carringtons Properties Limited | Extraterritorial | 2021 |
| Carruthers Aerospace Ltd | Manufacturing | 2017 |
| Carry Stones Limited | Manufacturing | 2025 |
| Carstairs Roofing Limited | Construction | 2019 |
| Carstar Auto Parts Co., Ltd | Wholesale & retail | 2023 |
| Cartainer Ltd | Construction | 2025 |
| Carter Mackenzie Limited | Administrative & support | 2000 |
| Carter Residential Limited | Real estate | 2018 |
| Carters Yard (UK) Ltd | Real estate | 2022 |
| Carve Construction Management Limited | Other services | 2021 |
| Carveron Consulting Ltd | Professional & scientific | 2024 |
| CAS Group Holdings Ltd | Financial services | 2003 |
| CAS Pathways Limited | Health & social care | 2025 |
| CAS Trade Nexus Co., Ltd | Wholesale & retail | 2024 |
| Casa D Paco Ltd | Information & communication | 2024 |
| Casa Maramureseana Ltd | Wholesale & retail | 2019 |
| Casa MIA Developments (NO 1) Limited | Construction | 2011 |
| Casa MIA Developments (NO 3) Limited | Construction | 2011 |
| Casa Tuscany Holdings Limited | Professional & scientific | 2018 |
| Cascades and Quayside Freehold Limited | Real estate | 2012 |
| Case Solved Wines Ltd | Wholesale & retail | 2012 |
| Casella Family Brands (Europe) Limited | Wholesale & retail | 1992 |
| Cashflow Freedom Compliance Limited | Professional & scientific | 2019 |
| Casies AC Limited | Professional & scientific | 2021 |
| Casmir Impex Ltd | Health & social care | 2023 |
| Casomo Ltd | Information & communication | 2023 |
| Cassa Properties Limited | Real estate | 2018 |
| Cassano Developments Limited | Real estate | 2004 |
| Cassia Properties Limited | Real estate | 2026 |
| Cassiabark Limited | Information & communication | 2011 |
| Cassini BIO Limited | Professional & scientific | 2025 |
| Castep Developers Group LLP | | 2018 |
| Castle Hill Ecology Ltd. | Professional & scientific | 2015 |
| Castle House Consultancy Limited | Professional & scientific | 2026 |
| Castle Manor & Ashby Fields Management Company Limited | Households | 2023 |
| Castle Marina Residents Association Limited | Households | 1987 |
| Castle Meadow (Management Company) Limited | Households | 2021 |
| Castle Point (Nottingham) Management Limited | Households | 2014 |
| Castle Recruitment Limited | Administrative & support | 2026 |
| Castle ST Barber Ltd | Other services | 2025 |
| Castleway Management Limited | Other services | 2017 |
| Castro Estates Limited | Real estate | 1999 |
| Cat Scaffolding (Cambridge) Limited | Construction | 2001 |
| Catalin Cucu Ltd | Health & social care | 2017 |
| Catalina Aircraft Limited | Arts & recreation | 2002 |
| Catalina Software Limited | Information & communication | 1997 |
| Catalysoft Limited | Information & communication | 2005 |
| Catalyst Creations Ltd | Wholesale & retail | 2023 |
| Catalyst-Bio Limited | Professional & scientific | 2013 |
| Catch Cell Therapy Consulting Ltd | Professional & scientific | 2026 |
| Catcheros Ltd | Administrative & support | 2026 |
| Cateboss Ltd | Wholesale & retail | 2025 |