| Caring People Limited | Administrative & support | 2004 |
| Caris Brook Ltd | Professional & scientific | 2003 |
| Carrington Management Company Limited | Real estate | 1988 |
| Carter Rose Properties Limited | Professional & scientific | 2014 |
| Castle Counselling Service Ltd | Health & social care | 2021 |
| Castle Hedingham Nursery Limited | Education | 2012 |
| Castle Skin Clinic Limited | Other services | 2017 |
| Caterers ETC Limited | Hospitality | 2018 |
| Cauvin Veterinary Consultancy Limited | Professional & scientific | 2012 |
| Cavadium Properties Limited | Real estate | 2017 |
| Cavendish Loft Conversions Ltd | Construction | 2005 |
| Cawicks Limited | Construction | 2006 |
| CC Resin Creations Ltd | Manufacturing | 2025 |
| CCK Coatings Limited | Construction | 2015 |
| CDT59 Industrial Ltd | Construction | 2024 |
| Cellcom Mobile Vehicle Solutions Limited | Manufacturing | 2015 |
| Central Ambulance Training Service Limited | Health & social care | 2017 |
| Central Park Enterprises Limited | Financial services | 2009 |
| Central Piling (Special Projects) Limited | Construction | 2025 |
| Central Piling Limited | Construction | 1980 |
| Centurion Braintree Limited | Real estate | 2005 |
| Certus Technologies Ltd. | Information & communication | 2000 |
| Chacheung Ltd | Professional & scientific | 2025 |
| Changing Directions Consulting UK Limited | Professional & scientific | 2023 |
| Charles Gardiner & SON Limited | Agriculture & fishing | 1955 |
| Charles Goddard Recruitment Ltd | Administrative & support | 2024 |
| Charlie's Painting and Building Ltd | Construction | 2025 |
| Charlotte Skin Specialist Ltd | Wholesale & retail | 2026 |
| Checkaface Limited | Information & communication | 2017 |
| Cherif Financial Services Limited | Financial services | 2021 |
| Chimney and Flue Services Limited | Extraterritorial | 2008 |
| Choat Holdings Limited | Financial services | 2023 |
| Choice Construction Limited | Construction | 1991 |
| Choice Fibre Optic Solutions Ltd | Information & communication | 2005 |
| Chris's Heating and Plumbing Services Ltd | Construction | 2017 |
| Christopher Anthony Estates Ltd | Real estate | 2025 |
| Christopher James Investments Limited | Real estate | 2022 |
| Christopher Kirk Thatching Limited | Construction | 2004 |
| Chuffedtobits Ltd | Professional & scientific | 2017 |
| Church View (Halstead) Management Company Limited | Households | 2009 |
| City & Country Roofing & Construction Limited | Construction | 2005 |
| City Link Couriers Ltd | Transport & logistics | 2021 |
| City PAY Associates Limited | Information & communication | 2005 |
| Claydon Creations Limited | Real estate | 1992 |
| Clean & Serene Group Limited | Administrative & support | 2024 |
| Clean and Serene Commercial Limited | Administrative & support | 2024 |
| Clean and Serene Homes Ltd | Administrative & support | 2025 |
| Clean Clear Skin Cosmetics Ltd | Wholesale & retail | 2024 |
| Clean Market Group Limited | Information & communication | 2024 |
| Clear Accounts Solutions Ltd | Professional & scientific | 2013 |
| Clearways Group Limited | Water & waste | 2026 |
| Cloakdean Limited | Transport & logistics | 1978 |
| Clubsuite Limited | Information & communication | 2014 |
| CM Dressage Ltd | Agriculture & fishing | 2021 |
| CMI Publishing Ltd. | Information & communication | 1999 |
| CO9 Senior Homehelp Limited | Health & social care | 2020 |
| CO9 West Car Sales Ltd | Wholesale & retail | 2013 |
| Coast to Coast Tipis Ltd | Administrative & support | 2020 |
| Cobain Digital Limited | Administrative & support | 2014 |
| Cobblers and Keys Ltd | Wholesale & retail | 2001 |
| Cocoa Canopy Limited | Manufacturing | 2010 |
| Coffee Kavern Limited | Administrative & support | 2017 |
| Coggeshall Pieces Management Company Limited | Households | 1989 |
| Colchard UK Ltd | Manufacturing | 2022 |
| Colchester Commercials Ltd | Wholesale & retail | 2025 |
| Colchester Home Improvements Ltd | Construction | 2024 |
| Cole & Ashville Limited | Professional & scientific | 2015 |
| COLLABOR8 AV Limited | Information & communication | 2013 |
| Collingwood Chiropractic Limited | Health & social care | 2015 |
| Colne Cargo Transport Services Limited | Transport & logistics | 1997 |
| Colne Construction Services Ltd | Construction | 2019 |
| Colne Electronics Limited | Manufacturing | 2008 |
| Colne Valley & Halstead Railway Company Limited | Transport & logistics | 1993 |
| Colne Valley Contracts Limited | Construction | 2004 |
| Colne Valley Home Help Ltd | Construction | 2024 |
| Come Find ME Ltd | Arts & recreation | 2016 |
| Comedy Card Company Ltd | Wholesale & retail | 2018 |
| Compass Energy Solutions Ltd | Professional & scientific | 2007 |
| Compass Real Estate Services Limited | Professional & scientific | 2008 |
| Complete Caravan Solutions Ltd | Manufacturing | 2010 |
| Concept Signs (Essex) Limited | Professional & scientific | 2006 |
| Concrete Floorfix Limited | Construction | 2015 |
| Concrete for Floors Ltd | Construction | 2023 |
| Connect-Financial Limited | Professional & scientific | 2018 |
| Connected Clouds Consultancy Limited | Professional & scientific | 2024 |
| Connor Property Services Ltd | Real estate | 2019 |
| Conservatory Solid Roofs Limited | Extraterritorial | 2010 |
| Consilium Hortus Ltd | Administrative & support | 2020 |
| Content Champion Limited | Information & communication | 2002 |
| Contractor Collins Ltd | Professional & scientific | 2026 |
| Controlled Systems Group Limited | Information & communication | 2026 |
| Coombe Lodge (Earls Colne) Maintenance Ltd | Households | 1991 |
| Cooper Grace Ltd | Professional & scientific | 2025 |
| Coppingdown Farm Management Company Limited | Real estate | 1998 |
| Core Facilities Maintenance Limited | Construction | 2025 |
| Coreshield Ltd | Construction | 1993 |
| Corporate Grounds Maintenance Ltd | Administrative & support | 2018 |
| Couchtrip Limited | Real estate | 2023 |
| Coukham Consulting Limited | Professional & scientific | 2012 |
| Country Manor Distribution Limited | Other services | 1990 |