| Copper & Oak Plumbing Ltd. Ltd | Households | 2026 |
| Copper Rose Cottage Limited | Real estate | 2024 |
| Coppice Gate 9RAYLEIGH) Management Company Limited | Households | 2005 |
| Copro Tuning Limited | Wholesale & retail | 2018 |
| Copsebriar Limited | Real estate | 1981 |
| Coquet Holdings Limited | Professional & scientific | 2021 |
| Cora Club Limited | Wholesale & retail | 2025 |
| Coram Children's Legal Centre Limited | Professional & scientific | 1980 |
| Coram Property Services Limited | Construction | 2011 |
| Cordcomply Limited | Professional & scientific | 2024 |
| Cordeiro Limited | Hospitality | 2018 |
| Core Atlantic North Limited | Administrative & support | 2017 |
| Core Construction Solutions Ltd | Construction | 2011 |
| Core Fusion Limited | Water & waste | 2010 |
| Core Fusion Recycling Limited | Water & waste | 2022 |
| Core Sports Management Ltd | Administrative & support | 2017 |
| Coreforge Ltd | Professional & scientific | 2025 |
| Corezo PAY Group Limited | Financial services | 2026 |
| Coriander Takeaway Limited | Hospitality | 2023 |
| Corinthian Square Residents Company Limited | Households | 1998 |
| Corium Medica Ltd | Health & social care | 2019 |
| Corium Properties Ltd | Real estate | 2025 |
| Cork’N CAP Ltd | Wholesale & retail | 2021 |
| Cornard Road Block "a" Management Company Limited | Households | 1990 |
| Cornard Road Block "B" Management Company Limited | Households | 1990 |
| Cornard Road Block "C" Management Company Limited | Households | 1990 |
| Cornard Road Block "E" Management Company Limited | Households | 1990 |
| Cornard Road Block "F" Management Company Limited | Households | 1990 |
| Cornard Road Block "G" Management Company Limited | Households | 1990 |
| Corncraft Limited | Wholesale & retail | 2006 |
| Cornelius Property Solutions Ltd | Real estate | 2021 |
| Corner Sofa Limited | Administrative & support | 2024 |
| Cornerstone Jaye Limited | Real estate | 2020 |
| Cornerstone Portfolio Investments Ltd | Financial services | 2015 |
| Cornerstone RE Ltd | Real estate | 2026 |
| Cornfield View Ltd | Construction | 2006 |
| Cornfields (Lakenheath) Residents Management Company Limited | Households | 2025 |
| Cornhill Property Services (East Anglia) Limited | Construction | 2020 |
| Corni 7 Limited | Other services | 2002 |
| Cornish Distributions Ltd | Wholesale & retail | 2019 |
| Corporate and Consumer Finance UK Limited | Extraterritorial | 2007 |
| Corporate Associates Limited | Financial services | 1987 |
| Corporate Building Management Ltd | Other services | 2024 |
| Corporate Connections Limited | Other services | 2020 |
| Corporate Investments Limited | Construction | 2011 |
| Corporate Recycling Solutions Ltd | Wholesale & retail | 2005 |
| Corporation Farms Limited | Real estate | 1978 |
| Corrosion Mitigation Limited | Professional & scientific | 2018 |
| Corte Medical Services Limited | Health & social care | 2016 |
| Corvalis Limited | Real estate | 2009 |
| Coscraft Limited | Wholesale & retail | 2010 |
| Cosmeducate Limited | Health & social care | 2012 |
| Cosmic Tattoo Limited | Other services | 2009 |
| Cosmosinc Accountancy Ltd | Professional & scientific | 2020 |
| COSTAN461 Ltd | Other services | 2022 |
| Costume and Play Ltd | Professional & scientific | 2017 |
| Cotswold RTM Company Limited | Households | 2012 |
| Cotswolds Prescriptions Limited | Wholesale & retail | 2018 |
| Cottage Landscapes Ltd | Administrative & support | 2023 |
| Cottee Highway & Transportation Consultants Limited | Transport & logistics | 1997 |
| Cottesmore Gardens Management Company Limited | Households | 2001 |
| Couldrey Consulting Limited | Information & communication | 2010 |
| Coulson Gardens Management Company Ltd | Real estate | 2022 |
| Counselling Solutions Consultancy Ltd | Administrative & support | 2013 |
| Count on US CIC | Professional & scientific | 2025 |
| Counterpoint Cleaning Limited | Administrative & support | 2017 |
| Counting House Consulting Ltd | Professional & scientific | 2012 |
| Country Plant Solutions Limited | Administrative & support | 2025 |
| Countryside Tree & Garden Services Ltd | Administrative & support | 2025 |
| County Broadband (EBT) Limited | Information & communication | 2023 |
| County Broadband Holdings Limited | Information & communication | 2013 |
| County Broadband Ltd | Information & communication | 2003 |
| County Contract Roofing Limited | Construction | 2002 |
| County Garage Conversions Limited | Construction | 2009 |
| County Supplies Limited | Transport & logistics | 2005 |
| Countywide Electrical Solutions Ltd | Construction | 2021 |
| Coupa Ltd | Manufacturing | 2006 |
| Court Property Company Limited | Hospitality | 1988 |
| Courtfield Contractors Limited | Professional & scientific | 2004 |
| Courthouse Residents Association Limited | Administrative & support | 2005 |
| Courtlands Management (Halstead) Ltd | Households | 1989 |
| Courtney Management Properties Ltd | Real estate | 2017 |
| Cove Springs Management Company Limited | Households | 2019 |
| Covenant Realty Limited | Real estate | 2025 |
| Covercourse Limited | Real estate | 1999 |
| Coverdale Barclay Limited | Professional & scientific | 2001 |
| Coverdale Specialist Flooring Limited | Construction | 2020 |
| Covertex Solutions Ltd | Education | 2013 |
| Cowabunga Pizza Ltd | Hospitality | 2018 |
| Cowdray Car Centre Limited | Wholesale & retail | 2012 |
| Cowdray Carpet Centre Limited | Wholesale & retail | 1989 |
| COX Design and Construction Limited | Administrative & support | 2012 |
| COX Group Holdings Ltd | Financial services | 2025 |
| COX Handy Home Services Ltd | Construction | 2021 |
| COX Landscapes Limited | Administrative & support | 1996 |
| Coyle Construction Limited | Construction | 2014 |
| Coyle Consultants Ltd | Information & communication | 2016 |
| Coyote Squared Limited | Professional & scientific | 2016 |
| Cozy Nail & Spa Ltd | Other services | 2026 |
| CP Barrett Telecoms Ltd | Information & communication | 2025 |