| Chairway to Heaven Essex Ltd | Other services | 2025 |
| Chalk Homes Limited | Real estate | 1984 |
| Chalvedon Medical Services Limited | Administrative & support | 2021 |
| Chambers Creative Limited | Professional & scientific | 2026 |
| Chameleon Asset Track Ltd | Extraterritorial | 2006 |
| Chameleon.Com Limited | Extraterritorial | 1999 |
| Chara Studio Limited | Extraterritorial | 2023 |
| Charfleets Van Sales Ltd | Wholesale & retail | 2024 |
| Charing Solutions Limited | Financial services | 2023 |
| Charmingcharmsco Ltd | Wholesale & retail | 2025 |
| Charnwood Enterprises Limited | Construction | 2015 |
| Chaskel Properties Ltd | Real estate | 2017 |
| Chay Supply Chain ORG Ltd | Wholesale & retail | 2024 |
| Cheeky Monkeys Play Limited | Arts & recreation | 2014 |
| Chella Ltd | Professional & scientific | 2019 |
| Chelmer Living Limited | Manufacturing | 2003 |
| Cherished Seven Enterprises Ltd | Real estate | 2023 |
| Chesterson Homes Ltd | Construction | 2019 |
| Chichester (Rawreth) Management Limited | Professional & scientific | 2014 |
| Chilli Addicts Ltd | Wholesale & retail | 2023 |
| Chilton Investments Limited | Real estate | 2005 |
| Chine Construction Ltd | Construction | 2026 |
| Christ Apostolic Church Pilgrims Tabernacle Ltd | Administrative & support | 2020 |
| Christiana Properties Limited | Real estate | 1980 |
| CIB Hub Ltd | Information & communication | 2024 |
| City Link Storage Ltd | Real estate | 2018 |
| City of Rome Ltd | Manufacturing | 2021 |
| City Servicing (London) Limited | Other services | 2010 |
| Cjde Homes Ltd | Real estate | 2023 |
| CJS Carpentry Joinery Shopfitting Limited | Manufacturing | 2024 |
| CJT Housing Ltd | Real estate | 2025 |
| CJW Carpentry Ltd | Manufacturing | 2023 |
| Claremount Views Ltd | Real estate | 2022 |
| Clarity Claims Ltd | Financial services | 2018 |
| Clarity Steel Services Limited | Construction | 2025 |
| Clark Building Contractors Limited | Construction | 2003 |
| Clark's Coatings Ltd | Construction | 2022 |
| Class a Property Solutions Ltd | Water & waste | 2025 |
| Class Muse Training Ltd | Education | 2026 |
| Classic Energy UK Ltd | Construction | 2019 |
| Claxton Homes Limited | Real estate | 2023 |
| Clean Car Centres Limited | Other services | 1992 |
| Clean Park Southend Limited | Administrative & support | 2017 |
| Cleaner the Betta Limited | Other services | 2005 |
| Cleaners World Limited | Water & waste | 2016 |
| Clippie Limited | Extraterritorial | 2018 |
| Clive's Consultancy Ltd | Professional & scientific | 2019 |
| CM9 Containers Ltd | Transport & logistics | 2025 |
| CMG Project Services Limited | Administrative & support | 2007 |
| CMG Property Solutions Limited | Real estate | 2023 |
| CMM Comm Services Limited | Professional & scientific | 2024 |
| CN Communications Limited | Information & communication | 2013 |
| CN Telecom Limited | Information & communication | 2013 |
| Cobra Lifting Services Ltd | Manufacturing | 2017 |
| Cobra Steel Services Limited | Construction | 2013 |
| Cobra Structures Limited | Other services | 2019 |
| Codewing Communications Limited | Extraterritorial | 1996 |
| Coker Services Ltd | Other services | 2022 |
| Collis Smith Limited | Manufacturing | 1985 |
| Collyer Fitted Furniture Ltd | Manufacturing | 2018 |
| Colosseum Stone and Building Services Limited | Construction | 2025 |
| Commercial Services & Property Limited | Other services | 2024 |
| Compasia United Kingdom Ltd | Other services | 2021 |
| Complete Facility Services Limited | Administrative & support | 2014 |
| Complete Intacare Hygiene Ltd | Wholesale & retail | 2007 |
| Completely K9 Hydrotherapy Limited | Other services | 2022 |
| Composite Kings Essex Ltd | Construction | 2024 |
| Composite South East Ltd | Construction | 2024 |
| Comrades Developments Limited | Construction | 2019 |
| Connell Waste Limited | Transport & logistics | 2022 |
| Consilium Negotiis Ltd | Professional & scientific | 2012 |
| Construction Plant & Logistics Register Ltd | Administrative & support | 2023 |
| Constructive Recycling Ltd | Water & waste | 2012 |
| Contact Electric Ltd | Construction | 2023 |
| Continental Build Ltd | Construction | 2020 |
| Conversion Fitting Services Limited | Construction | 2001 |
| Coogee Developments Limited | Construction | 2023 |
| Coogee Trading Limited | Construction | 2019 |
| Cooks Construction (South) Ltd | Construction | 2018 |
| Cooper Steel and Welding Services Ltd | Administrative & support | 2018 |
| Copperfield Contracts Ltd | Professional & scientific | 2023 |
| Copperfield Holiday Park Limited | Hospitality | 2015 |
| Coreflow Systems Limited | Information & communication | 2026 |
| Corefreight Distribution Limited | Transport & logistics | 2025 |
| Corefresh Bar and Grill Limited | Extraterritorial | 2015 |
| Corefresh Limited | Wholesale & retail | 2009 |
| Corefruit Limited | Extraterritorial | 2014 |
| Coreveg Limited | Wholesale & retail | 2013 |
| Cornbloom Properties Ltd | Real estate | 2024 |
| Cornelius Vermuyden School | Education | 2013 |
| Coronet Peak Time-Share Limited | Extraterritorial | 1982 |
| Correct Routes Limited | Other services | 2021 |
| Correctly Books Ltd | Professional & scientific | 2025 |
| Cose Belle Limited | Wholesale & retail | 2024 |
| Countryfield Properties Ltd | Construction | 2021 |
| Countryside Estates (Essex) Limited | Real estate | 2019 |
| Countryside Estates (Lettings) Ltd | Real estate | 2024 |
| Countryside Estates (Sales) Ltd | Real estate | 2019 |
| Cous Car Sales Ltd | Wholesale & retail | 2020 |
| Coverwell Services Limited | Construction | 2011 |