| Costarellos UK Limited | Manufacturing | 2017 |
| Costina Landscape Ltd | Administrative & support | 2021 |
| Cosy HUT Ltd | Real estate | 2020 |
| Coucou Ltd | Wholesale & retail | 2011 |
| Counting Kids Franchising Ltd | Education | 2021 |
| County Cars Ltd | Wholesale & retail | 2018 |
| County Sprayers Ltd | Wholesale & retail | 2024 |
| Courtenay Holdings (South East) Limited | Financial services | 2013 |
| Courtenay Homes Limited | Professional & scientific | 2013 |
| Courtier and Courtier Ltd | Professional & scientific | 2018 |
| Cousins Cars Ltd | Transport & logistics | 2023 |
| Cousins Farms Limited | Agriculture & fishing | 1957 |
| Covenbrook Fabrications Limited | Extraterritorial | 1978 |
| Covenbrook Limited | Extraterritorial | 2014 |
| Coxs Yard Management Company Limited | Households | 2025 |
| Cozy Canine Cottage Ltd | Agriculture & fishing | 2025 |
| Cozy MAE Studios Ltd | Information & communication | 2024 |
| CPD Management Ltd | Construction | 2026 |
| CPJ Projects Limited | Professional & scientific | 2014 |
| Crafted Records Ltd | Extraterritorial | 2024 |
| Crafted Studios Ltd | Information & communication | 2023 |
| Craig Platt Consulting Ltd | Information & communication | 2024 |
| Cranston Holdings Ltd | Financial services | 2025 |
| Craufurd Cooper Limited | Administrative & support | 2017 |
| Crawford Creative Technology Ltd | Information & communication | 2009 |
| CRB & Family Limited | Wholesale & retail | 2023 |
| Createbritain Partnership Limited | Arts & recreation | 2013 |
| Creative Sun Limited | Administrative & support | 2022 |
| Credence Installations Ltd | Energy | 2019 |
| Crescent Retail Design Limited | Construction | 2016 |
| Critical Care Solutions Ltd. | Health & social care | 2017 |
| Crocs Catering Equipment Ltd | Administrative & support | 2019 |
| Croft Bathrooms Ltd | Construction | 2021 |
| Crofters Mead (Black Notley) Management Company Limited | Households | 1999 |
| Crop Salons Ltd | Other services | 2019 |
| Crosier Place Limited | Households | 2018 |
| Crossbow Construction Limited | Construction | 2014 |
| Crossfly Limited | Wholesale & retail | 2020 |
| Crossroads Braintree and Chelmsford Ltd | Other services | 1996 |
| Crown Commercial Maintenance Ltd | Other services | 2019 |
| Crown Group International Ltd | Wholesale & retail | 2023 |
| Crown Hire Ltd | Administrative & support | 2018 |
| Crowned Crane Limited | Real estate | 2026 |
| Crypto Agent Ltd | Information & communication | 2026 |
| CS Motorsports Ltd | Wholesale & retail | 2023 |
| CSB Electrical Contractors Limited | Construction | 2017 |
| CSC Cleaning Solutions Limited | Administrative & support | 2024 |
| CSD Network Services Ltd | Information & communication | 2001 |
| Csfm Services Limited | Administrative & support | 2023 |
| CSP Resources Limited | Professional & scientific | 2013 |
| Cube Empire Properties Limited | Real estate | 2021 |
| CUE - SD Limited | Arts & recreation | 2003 |
| Cult Status Ltd | Real estate | 2010 |
| Cultures United Living Together Ltd | Administrative & support | 2020 |
| Cunningtons LLP | | 2014 |
| Curby Construction Ltd | Construction | 2024 |
| Curd Hall Limited | Construction | 2017 |
| Curry House Braintree Limited | Hospitality | 2026 |
| Curry Nights Braintree Ltd | Hospitality | 2021 |
| Currybox Braintree Limited | Hospitality | 2024 |
| Curtain Maid Holdings Ltd | Financial services | 2018 |
| Curtis Murray Associates Limited | Administrative & support | 2015 |
| Curtis Signs (Braintree) Limited | Manufacturing | 2014 |
| Custom Colors and Consulting Ltd | Construction | 2026 |
| CUT Above Construction Ltd | Construction | 2018 |
| CVB Accounts Limited | Professional & scientific | 2007 |
| CVN Trans Ltd | Transport & logistics | 2016 |
| CWB Electrical Services Ltd | Construction | 2023 |
| Cwcs Investments Limited | Financial services | 2023 |
| Cwcs Property Limited | Financial services | 2023 |
| Cybehave Ltd | Information & communication | 2025 |
| Cyber Dave Ltd | Information & communication | 2024 |
| Cybertech.Investments Ltd | Financial services | 2025 |
| Cyberv Limited | Professional & scientific | 2025 |
| Cyjay Limited | Real estate | 2013 |
| CYM Consulting Limited | Information & communication | 2002 |
| Cyrano Holdings Limited | Professional & scientific | 2002 |
| Cyrano Limited | Wholesale & retail | 1998 |
| Cyrano Properties Limited | Professional & scientific | 2002 |
| D & H Electrics Limited | Construction | 2018 |
| D & J Plumbing & Heating (UK) Ltd | Construction | 2013 |
| D and D Building Services Ltd | Construction | 2015 |
| D D Colberts Limited | Construction | 2024 |
| D E T Scaffolding Limited | Construction | 2004 |
| D Groundworks Ltd | Construction | 2020 |
| D Howard Electrical Limited | Construction | 2017 |
| D J Developments Ltd | Construction | 2005 |
| D L S Computers Limited | Information & communication | 2010 |
| D M Drainage Ltd | Water & waste | 2013 |
| D Metcalf Interiors Limited | Construction | 2006 |
| D Watson Limited | Construction | 2006 |
| D&G Bespoke Installs Ltd | Construction | 2026 |
| D&J Group Ltd | Wholesale & retail | 2024 |
| D&L Managed Services Limited | Administrative & support | 2021 |
| DAC Planning Limited | Administrative & support | 2016 |
| Dagley & Dawson Ltd | Construction | 2011 |
| Dahan Properties Limited | Real estate | 2009 |
| Daijo Holdings Limited | Professional & scientific | 2016 |
| Dammyteb Ltd | Health & social care | 2021 |
| DAN Tilling World Limited | Construction | 2019 |