| C.K.G. Contracts Limited | Water & waste | 1989 |
| C.N.D Food & Wine Ltd | Wholesale & retail | 2022 |
| C.V.I Insurance Services Limited | | 1987 |
| Cabana Soft Drinks (Essex) Limited | Wholesale & retail | 1977 |
| Cablezoom Limited | Information & communication | 1996 |
| CAD Coordination Limited | Professional & scientific | 2003 |
| CAD Coordination Services Limited | Extraterritorial | 2003 |
| CAD Drafting Services Limited | Extraterritorial | 2003 |
| CAD Enterprise Ltd | Information & communication | 2002 |
| CAD Link Services Limited | Extraterritorial | 2003 |
| CAD Project Services Limited | Extraterritorial | 2003 |
| CAD Surveying Limited | Extraterritorial | 2003 |
| CAD Surveying Services Limited | Extraterritorial | 2003 |
| CAD Technical Services Limited | Extraterritorial | 2005 |
| CAD Tracing Limited | Extraterritorial | 2003 |
| CAD Tracing Services Limited | Extraterritorial | 2003 |
| Cadrick Samuel Ltd | Wholesale & retail | 2025 |
| Cafe 1989 Ltd | Hospitality | 2020 |
| Cagaluchie (Madame) Limited | | 1983 |
| Cage Properties Limited | Construction | 2006 |
| CAH Commerce Ltd | Wholesale & retail | 2023 |
| Cahill Plumbing & Heating Ltd | Construction | 2019 |
| Cakesand Ltd | Hospitality | 2015 |
| Calcott Hall Limited | Wholesale & retail | 2004 |
| Calcwin Limited | Information & communication | 2026 |
| Caldare House Limited | Real estate | 1949 |
| Caliba Limited | Professional & scientific | 2019 |
| Calibre Homes (Essex) Ltd | Construction | 2017 |
| Callaway & Sons Insurance Consultants Limited | Financial services | 2000 |
| Callaway Contracts Limited | Construction | 2006 |
| Callaway Sykes Associates Limited | Financial services | 1971 |
| Callclear Limited | Construction | 2005 |
| Calyx Architecture Ltd | Professional & scientific | 2017 |
| Calyx Assets Ltd | Real estate | 2019 |
| Cambria Estates Limited | Construction | 1995 |
| Cambridge Agricultural Ltd | Manufacturing | 2001 |
| Camden Cart Ltd | Wholesale & retail | 2026 |
| Cameleon Gardens Limited | Administrative & support | 2002 |
| Camfaud Concrete Pumps Limited | Construction | 1991 |
| Camillia Limited | | 1987 |
| Camp Garage (Colchester) Limited | Real estate | 1963 |
| Can'T Stop Scaffolding Ltd | Construction | 2023 |
| Candlelight Craft Limited | Wholesale & retail | 2007 |
| Candymishka Limited | Manufacturing | 2024 |
| Canine Culture Ltd | Wholesale & retail | 2023 |
| Canopy Property Investments Ltd | Real estate | 2026 |
| Cantatar Ltd | Wholesale & retail | 2026 |
| Cantle Limited | Administrative & support | 2002 |
| Canvey Skip Hire Limited | Extraterritorial | 1993 |
| CAP247 Recruitment Agency Limited | Administrative & support | 2019 |
| Capax Services Ltd | Professional & scientific | 2003 |
| Capelo Limited | Information & communication | 2013 |
| Capital Audiology Limited | Health & social care | 2002 |
| Capital Car Cleaning Co Limited | Administrative & support | 2005 |
| Capital Civil Engineering Limited | | 1986 |
| Capital Construction Essex Ltd | Construction | 2021 |
| Capital Fire and Security Limited | Administrative & support | 2003 |
| Capital Mortgages and Finance Limited | Wholesale & retail | 2020 |
| Capital Plumbing & Heating Merchants Ltd | Wholesale & retail | 2001 |
| Capital Power & Data Limited | Construction | 2007 |
| Capital Pumps Ltd | Manufacturing | 2021 |
| Capri Mechanical Services Limited | Construction | 1974 |
| Car Dome Ltd | Wholesale & retail | 2023 |
| Caramelo Kids Ltd | Manufacturing | 2018 |
| Carbonfoam Engine Solutions Ltd | Manufacturing | 2025 |
| Carcelona Limited | Wholesale & retail | 2003 |
| Cardiwillow Ltd | Wholesale & retail | 2024 |
| Care Construction (Surrey) Limited | Construction | 1996 |
| Career-Sos Limited | Hospitality | 2005 |
| Careers Connect Global Ltd | Administrative & support | 2023 |
| Caremax Ltd | Education | 2018 |
| Caresford Estates Ltd | Real estate | 2025 |
| Cargate Limited | Other services | 2025 |
| Caring Limited | | 1980 |
| Caringg Ltd | Health & social care | 2022 |
| Carlek Auto Electrical Limited | Wholesale & retail | 2003 |
| Carlines Limited | Professional & scientific | 1984 |
| Carlton Shoes Limited | Manufacturing | 1990 |
| Carlton Tyres (Rainham) Limited | Other services | 2002 |
| Carlton Tyres Limited | Wholesale & retail | 2003 |
| Carlux Pro Limited | Wholesale & retail | 2026 |
| Carnall Landscapes Limited | Administrative & support | 1998 |
| Carnivox Ltd | Wholesale & retail | 2026 |
| Carpenter & Oakley Associates Ltd | Professional & scientific | 2000 |
| Carpet Force (UK) Limited | Wholesale & retail | 1993 |
| Carpet Sense (UK) Limited | Professional & scientific | 1993 |
| Carrera Homes Limited | | 1988 |
| Carross Shopfitting UK Limited | Construction | 2024 |
| Carrotop Limited | Hospitality | 2017 |
| Carrylift (Essex) Limited | Wholesale & retail | 2000 |
| Cartcraze Enterprises Ltd | Wholesale & retail | 2024 |
| Cartel Brickwork and Building Contractors Limited | Construction | 2003 |
| Cartelloa Ltd | Wholesale & retail | 2026 |
| Carter Glass Limited | Construction | 2009 |
| Carter Knott Holdings Ltd | Hospitality | 2024 |
| Cartova Ltd | Wholesale & retail | 2026 |
| Casa Iberica Fine Foods Limited | Wholesale & retail | 2015 |
| Casas DE RAE Ltd | Real estate | 2025 |
| Case Consultant Solutions Ltd | Professional & scientific | 2016 |
| Cash Received Ltd | Professional & scientific | 2001 |