| Club Cultured Ltd | Hospitality | 2018 |
| Club Management Systems Ltd | Administrative & support | 2023 |
| Club One Hundred 30:30 Ltd | Administrative & support | 2016 |
| Club One Hundred Darryl Stone Ltd | Education | 2010 |
| Club One Hundred Mark Ltd | Education | 2010 |
| Club One Hundred Matthew Ltd | Education | 2010 |
| Club One Hundred MWE Ltd | Administrative & support | 2017 |
| Clubentis Ltd | Information & communication | 2026 |
| CM Commercial Lettings Ltd | Real estate | 2022 |
| CM Law Recruitment Limited | Administrative & support | 2025 |
| CM7 Cleaning Services Ltd | Administrative & support | 2022 |
| CMA Solutions Limited | Professional & scientific | 2025 |
| Cmaer Ltd | Manufacturing | 2025 |
| CMB Cost Consultants Ltd | Professional & scientific | 2010 |
| CMS Sealants Limited | Other services | 2003 |
| CMW Golf Equipment Limited | Wholesale & retail | 2016 |
| CN (Essex) Limited | Extraterritorial | 2018 |
| CN Polishing Limited | Construction | 2015 |
| CNF London Ltd | Public administration | 2023 |
| CNM Studio Limited | Arts & recreation | 2020 |
| Coach Direct Limited | Transport & logistics | 1997 |
| Coach Roach Soccer Limited | Arts & recreation | 2015 |
| Coast Event Management Ltd | Administrative & support | 2026 |
| Coast Nova Ltd | Construction | 2024 |
| Coastal Coaching Ltd | Professional & scientific | 2017 |
| Coastal Exchange Ltd | Wholesale & retail | 2024 |
| Coastal Group Ltd | Financial services | 2025 |
| Coastal Maintenance Limited | Construction | 2023 |
| Coastal Payroll Limited | Administrative & support | 2025 |
| Coastal Wealth Ltd | Information & communication | 2025 |
| Cobat Secretarial Services Limited | Financial services | 2000 |
| Cobbold Cameras Ltd | Information & communication | 2023 |
| Coco and BLU Limited | Manufacturing | 2020 |
| Coco Beauty Salon Ltd | Other services | 2014 |
| Cocreate Vision Limited | Arts & recreation | 2023 |
| Code Food Consulting Ltd | Hospitality | 2015 |
| CODE7 Fire Resilience Ltd | Financial services | 2026 |
| Coding Warehouse Limited | Information & communication | 2019 |
| Coeth Limited | Manufacturing | 2025 |
| Coffee Capsule UK Ltd | Manufacturing | 2021 |
| Coffee Station (Rayleigh) Limited | Hospitality | 2025 |
| Cognify Global UK Ltd | Professional & scientific | 2024 |
| Cohesive Consulting Ltd | Professional & scientific | 2022 |
| Cole Group Ltd | Construction | 2015 |
| Cole Trade Supplies Ltd | Wholesale & retail | 2023 |
| Cole-Levi Klimt Ltd | Wholesale & retail | 2023 |
| Colebys London Limited | Wholesale & retail | 2023 |
| Colin Alexander Limited | Extraterritorial | 2023 |
| Collective Property Services Limited | Real estate | 2017 |
| Collectors & Recycling Ltd | Water & waste | 2025 |
| Collier Mechanical Services Ltd | Construction | 2015 |
| Collings Investments Limited | Hospitality | 2024 |
| Collissions (Essex) Limited | Wholesale & retail | 2011 |
| Colne View RTM Company Limited | Households | 2003 |
| Colorado Builders Ltd | Construction | 2013 |
| Colossal Network Educational Services Ltd | Education | 2025 |
| Colour Connections Limited | Wholesale & retail | 2004 |
| Colour Trim Ltd | Construction | 2021 |
| Colourful Zebra Limited | Extraterritorial | 2023 |
| Columbia Wharf (Block a) Management Company Limited | Administrative & support | 1996 |
| Colux Chain Limited | Administrative & support | 2025 |
| Colux Global Limited | Administrative & support | 2024 |
| Colux Holding Ltd | Real estate | 2021 |
| Colux Properties Limited | Real estate | 2024 |
| Combat Academy for Sports Limited | Other services | 2018 |
| Combined Communications (Essex) Limited | Information & communication | 1992 |
| Comestic Cleaning Limited | Administrative & support | 2024 |
| Comfort Home Improvements Limited | Construction | 2024 |
| Comic Book UK CIC | Other services | 2024 |
| Coming UP Roses Ltd | Other services | 2024 |
| Comm Space Limited | Other services | 2012 |
| Commander Air-Conditioning Limited | Extraterritorial | 2024 |
| Commander Building Services Limited | Construction | 2013 |
| Commander Fire Protection Limited | Administrative & support | 2024 |
| Commander Investments Limited | Financial services | 2019 |
| Commander Properties Limited | Real estate | 2019 |
| Commercial Street (Norton) Management Company Limited | Households | 2018 |
| Company of Financial and Management Accountants Limited | Professional & scientific | 2018 |
| Compass Long Term Lets Limited | Real estate | 2025 |
| Compass Social Care Limited | Hospitality | 2021 |
| Compassion Missions UK CIC | Health & social care | 2026 |
| Complete Construction (GB) Ltd | Construction | 2010 |
| Complete Drives and Patios Ltd | Construction | 2014 |
| Complete English Kitchens Ltd | Manufacturing | 2008 |
| Complete Plastering and Drylining Limited | Construction | 2020 |
| Complete Property Maintenance (Essex) Ltd | Construction | 2023 |
| Complete Waste Management Ltd | Water & waste | 2023 |
| Complete Waterproofing Services Limited | Construction | 2012 |
| Comproof Ltd | Construction | 2017 |
| Compton Partners Limited | Wholesale & retail | 2008 |
| Comstation Limited | Other services | 2000 |
| Concept Facades Limited | Construction | 2021 |
| Conceptarch Ltd | Professional & scientific | 2016 |
| Concord (London) Limited | Professional & scientific | 1992 |
| Confident Theatre Company Ltd | Arts & recreation | 2026 |
| Connect 4 Security Limited | Administrative & support | 2016 |
| Connect EDU Limited | Education | 2019 |
| Connectability CIC | Health & social care | 2020 |
| Connected by Courtney Limited | Administrative & support | 2018 |
| Connectif Technology Limited | Information & communication | 2017 |