| Cleo Capital Limited | Administrative & support | 2025 |
| Cleveland Internet Services Limited | Professional & scientific | 1995 |
| Cleversport Limited | Administrative & support | 2001 |
| Click Evolve Limited | Professional & scientific | 2025 |
| Clickreach Limited | Professional & scientific | 2016 |
| Clientline Accountancy-Financial Consultancy Ltd. | Professional & scientific | 2014 |
| Clientline Tax Limited | Professional & scientific | 2023 |
| Clifflane Limited | Real estate | 1985 |
| Clift Controls Limited | Manufacturing | 1978 |
| Clippin Gorgeous Ltd | Other services | 2023 |
| Clir Limited | Transport & logistics | 2022 |
| Clohessy Building Services Ltd | Administrative & support | 2026 |
| Close Circuit Security Services Limited | Construction | 2021 |
| Cloud Nine Voice and Data Ltd | Information & communication | 2019 |
| Clwyd Internet Services Limited | Professional & scientific | 1995 |
| CM Flooring Supplies Ltd | Construction | 2022 |
| CM PE Consultancy Ltd | Education | 2021 |
| CM Workforce Solutions Limited | Other services | 2005 |
| CM8 Properties Limited | Real estate | 2022 |
| CMD Ceilings Limited | Construction | 2003 |
| CMI Analytics Limited | Professional & scientific | 2019 |
| Cmst Limited | Financial services | 2018 |
| Coach House Way (Witham) Management Limited | Real estate | 2010 |
| Coachpt ME Ltd | Information & communication | 2025 |
| Cobra Electrical Services Ltd | Construction | 2016 |
| Code Security Ltd | Administrative & support | 2023 |
| Codestep (UK) Limited | Information & communication | 2021 |
| Coggeshall Community BUS Limited | Transport & logistics | 1991 |
| Colchester Windows & Doors Ltd | Construction | 2024 |
| Collidescope CIC | Arts & recreation | 2024 |
| Colliers Body Builders Limited | Professional & scientific | 2002 |
| Colliers TB Holdings Ltd | Professional & scientific | 2022 |
| Colliers Truck Builders Limited | Manufacturing | 2000 |
| Colliers Truck Investments Ltd | Professional & scientific | 2022 |
| Colne Valley Funeral Service Limited | Other services | 2000 |
| Colne Valley Properties Limited | Construction | 1989 |
| Colpjs IT Limited | Information & communication | 2020 |
| Colton Joinery Limited | Construction | 2025 |
| Combi Construction Limited | Construction | 2017 |
| Combined Property Maintenance Limited | Construction | 2020 |
| Combipanel Limited | Administrative & support | 2020 |
| Comfort Water Hygiene Limited | Water & waste | 2016 |
| Comfort Water Treatment Limited | Water & waste | 2016 |
| Commodity Centre (Group) Limited | Financial services | 2012 |
| Commodity Centre Europe Limited | Transport & logistics | 2016 |
| Commodity Centre Falcon Terminal Limited | Real estate | 2018 |
| Commodity Centre Limited | Transport & logistics | 2005 |
| Commodity Centre Osprey Holdings Limited | Financial services | 2020 |
| Commodity Centre Osprey Terminal Limited | Financial services | 2020 |
| Commodity Centre Property Holdings Limited | Real estate | 2018 |
| Commodity Centre UK Limited | Transport & logistics | 1992 |
| Commodity Store Limited | Transport & logistics | 2017 |
| Comms Install Limited | Information & communication | 2016 |
| Community Foods (Holdings) Limited | Wholesale & retail | 2012 |
| Community Foods Limited | Wholesale & retail | 1977 |
| Compact Paving Limited | Construction | 2020 |
| Complete Dance Studios Limited | Education | 2019 |
| Compliance Alliance Limited | Extraterritorial | 2022 |
| Compliant Solutions Limited | Professional & scientific | 2000 |
| Concordia Chartered Loss Adjusters Ltd | Financial services | 2012 |
| Concordia Compliance Ltd | Professional & scientific | 2012 |
| Concordia Consultancy Ltd | Financial services | 2003 |
| Concordia Global Network Limited | Financial services | 2009 |
| Concordia Legal Limited | Professional & scientific | 2009 |
| Concordia Risk Ltd | Financial services | 2012 |
| Consultancy by Fenttiman Ltd | Information & communication | 2014 |
| Copp Consultants Ltd | Professional & scientific | 2024 |
| Coppermill Properties Limited | Real estate | 2019 |
| Cor-Line Systems Ltd | Manufacturing | 2025 |
| Corkerry Ltd | Construction | 2017 |
| Corner House Care Limited | Administrative & support | 2010 |
| Cornersquare Construction Limited | Construction | 2024 |
| Cornerstone Home Services Limited | Construction | 2026 |
| Cornwall Internet Services Limited | Professional & scientific | 1995 |
| Correct Home Moves Ltd | Real estate | 2024 |
| Cosmic Flow Limited | Financial services | 2019 |
| Coterie Talent Limited | Professional & scientific | 2024 |
| Cottage Green (Silverend) Resident Management Company Limited | Households | 1996 |
| Countrywide Conservatories UK Limited | Construction | 2003 |
| Countrywise Animal Supplies Ltd | Wholesale & retail | 2010 |
| County Internet Services Limited | Information & communication | 1995 |
| Couro Accessories Limited | Manufacturing | 2023 |
| Courtney Lang Limited | Construction | 2010 |
| CPC Trading Limited | Wholesale & retail | 2014 |
| CPR 1 Leisure Limited | Administrative & support | 2017 |
| Crafty Bear Kitchen Ltd | Hospitality | 2023 |
| Craig Browne Homes Limited | Real estate | 2018 |
| Crazy Divas Limited | Other services | 2003 |
| Creative Stays Limited | Administrative & support | 2021 |
| Credence Connections UK Ltd | Wholesale & retail | 2024 |
| Cremation Reclaim Limited | Water & waste | 2021 |
| Crescent Property Assets Limited | Real estate | 2015 |
| Crestnet Technology Limited | Information & communication | 2021 |
| Creswell Murray Ltd | Financial services | 2024 |
| Critical Facilities Solutions Limited | Construction | 2018 |
| Crofters at the Courtyard Limited | Hospitality | 2025 |
| Crowdestates Limited | Financial services | 2013 |
| Crowdestates Security Trustee Limited | Financial services | 2016 |
| Crown Alliance Ltd | Information & communication | 2026 |
| Crown Dental Supply Limited | Wholesale & retail | 2022 |