| Clark Electric Clutch & Controls Limited | Professional & scientific | 1961 |
| Clark Heating and Plumbing Ltd | Construction | 2012 |
| Classics and Cruisers Ltd | Wholesale & retail | 2021 |
| Clays Menswear Limited | Wholesale & retail | 2021 |
| Clear Clog Ltd | Water & waste | 2025 |
| Clear Lane Consulting Limited | Professional & scientific | 2024 |
| Clear Payment Limited | Other services | 2022 |
| Clearing Space Limited | Professional & scientific | 2010 |
| Click & Correct Chiropractic Ltd | Health & social care | 2022 |
| Clipper Aviation Limited | Education | 2012 |
| Clive Thompson Property Development Ltd. | Real estate | 2001 |
| Cloud 21 Limited | Professional & scientific | 2009 |
| Cloud Hive Accounting Ltd | Professional & scientific | 2020 |
| Cloudsync Limited | Information & communication | 2022 |
| CM Franchise Limited | Wholesale & retail | 2018 |
| Cnem Roofing & Guttering Limited | Construction | 2022 |
| Cnpl MEP Limited | Financial services | 2021 |
| Coaching and Change Limited | Professional & scientific | 2001 |
| Coco & Bloom Limited | Wholesale & retail | 2018 |
| Coggeshall Mills Resident Association Limited | Households | 2022 |
| Cold Circles Property Limited | Real estate | 2025 |
| Colette Ltd | Manufacturing | 2021 |
| Collaborative Thinking Ltd | Professional & scientific | 2026 |
| Collier Security Systems Ltd | Administrative & support | 2025 |
| Collins Cardiac Services Limited | Health & social care | 2008 |
| Colour Coatings (South East) Limited | Manufacturing | 2002 |
| Comfort Air Solutions Ltd | Energy | 2023 |
| Commercial Buyers Group Limited | Wholesale & retail | 2015 |
| Commercial Services Education Holdings Ltd | Financial services | 2004 |
| Commercial Services Education Ltd | Education | 1988 |
| Commercial Services Kent Limited | Water & waste | 2006 |
| Commercial Services Trading Ltd | Administrative & support | 2006 |
| Commercial Ventures UK Limited | Real estate | 2005 |
| Community Stewardship and Placemakers Ltd | Professional & scientific | 2025 |
| Compagnie Fruitiere UK Limited | Wholesale & retail | 1969 |
| Conditioning House RTM Company Limited | Households | 2023 |
| Conisborough Management Company Limited | Households | 2026 |
| Consolidated Education Supplies Limited | Information & communication | 2024 |
| Construct Media Inc Ltd | Professional & scientific | 2024 |
| Construction and Inspection Limited | Construction | 2010 |
| Convar Europe Limited | Wholesale & retail | 1992 |
| Convar Holdings Europe Limited | Financial services | 1992 |
| Cooke and Lock Developments Ltd | Real estate | 2020 |
| Cooke and Lock Ltd | Construction | 2015 |
| Copenhagen Place Trowe’S Lane Swallowfield RMC Limited | Households | 2026 |
| Cora Health Diagnostics Ltd | Health & social care | 2001 |
| Cora Health Ltd | Administrative & support | 2009 |
| Cora Health Northampton Clinic Ltd | Health & social care | 2005 |
| Cora Health Norwich Clinic Ltd | Health & social care | 2005 |
| Corinna Grant Consulting Ltd | Professional & scientific | 2022 |
| Cosmic Disco Apparel Ltd | Wholesale & retail | 2026 |
| Cottons Landing Management Limited | Households | 1989 |
| Countryside Developments Limited | Extraterritorial | 1968 |
| Countryside Partnerships Southern Limited | Construction | 1989 |
| Countryside Partnerships Southern NO.1 Limited | Real estate | 1994 |
| Countryside Properties (Special Projects) Limited | Professional & scientific | 1992 |
| Countryside Properties (Strategic Land) Limited | Construction | 2020 |
| Courtyard Management (Ryarsh) Limited | Households | 2008 |
| Couzo Holdings Ltd | Financial services | 2026 |
| COX Electrical Contractors Ltd | Construction | 2026 |
| COX Property Investments Group Limited | Real estate | 2026 |
| COX UK Property LLP | | 2022 |
| Cozy Controllers Ltd | Manufacturing | 2025 |
| CR02QZ Limited | Construction | 2022 |
| Creative Gifts Ltd | Manufacturing | 2013 |
| Creative Wire Limited | Professional & scientific | 2011 |
| Creek Homes Ltd | Real estate | 2019 |
| Crewe Lane Kenilworth JV LLP | | 2019 |
| Crhservices Limited | Professional & scientific | 2018 |
| Crofters Mead Management Limited | Households | 1968 |
| Croham Investments Limited | Real estate | 1956 |
| Crossbill Ltd | Information & communication | 2016 |
| Crossbill Properties Ltd | Real estate | 2022 |
| Crucible Topco Limited | Financial services | 2026 |
| Crxss Design Ltd | Administrative & support | 2022 |
| Crystalclear Management Limited | Hospitality | 2021 |
| CSG Global Education Ltd | Wholesale & retail | 1983 |
| CT2 Plastering and Rendering Limited | Construction | 2026 |
| CTB Capital Partners Limited | Professional & scientific | 2019 |
| CTK Europe Ltd | Professional & scientific | 2018 |
| Ctlfiregroup Ltd | Professional & scientific | 2025 |
| Cultivate Homes Ltd | Construction | 2018 |
| Curiosity Works Ventures Limited | Professional & scientific | 2025 |
| Cutty Holdings Limited | Financial services | 2020 |
| CWB Property Maintenance Ltd | Construction | 2018 |
| Cwichelm Limited | Administrative & support | 2010 |
| Cyberbyte Software Ltd | Information & communication | 2020 |
| Cycle Smart Co Ltd | Health & social care | 2018 |
| Cygnet (DH) Limited | Health & social care | 2013 |
| Cygnet (OE) Limited | Health & social care | 1999 |
| Cygnet 2002 Limited | Health & social care | 2002 |
| Cygnet Aspirations Developments Limited | Health & social care | 2009 |
| Cygnet Behavioural Health Limited | Health & social care | 2000 |
| Cygnet Care Services Limited | Health & social care | 1992 |
| Cygnet Clifton Limited | Health & social care | 2008 |
| Cygnet Consulting Ltd | Professional & scientific | 2016 |
| Cygnet Health Care Limited | Health & social care | 1987 |
| Cygnet Health Developments Limited | Construction | 2016 |
| Cygnet Health Properties Limited | Real estate | 2016 |
| Cygnet Health UK Limited | Health & social care | 2008 |