| Cloud Runner Limited | Information & communication | 2022 |
| CLOUD7 Air Fresheners Ltd | Manufacturing | 2025 |
| Cloudberry Children Care Services Ltd | Health & social care | 2026 |
| Club Hush Ltd | Professional & scientific | 2026 |
| Club Sportif Limited | Administrative & support | 1989 |
| CLUB72 Golf Limited | Wholesale & retail | 2023 |
| Clucky Wings Holdings Ltd | Financial services | 2026 |
| Clucky Wings Ltd | Hospitality | 2024 |
| Clyvora Ltd | Wholesale & retail | 2026 |
| CM Garden & Tree Care Ltd | Administrative & support | 2020 |
| CM Hoodstore Ltd | Wholesale & retail | 2021 |
| CM Investments Limited | Real estate | 2024 |
| CM Pharm Ltd | Wholesale & retail | 2021 |
| CM Psychology Limited | Education | 2021 |
| Cmschenk Ltd | Wholesale & retail | 2025 |
| CMT Cars Ltd | Administrative & support | 2025 |
| CMZ Meats Limited | Wholesale & retail | 2022 |
| CNA Properties Limited | Real estate | 2022 |
| CNE Concepts Ltd | Transport & logistics | 2015 |
| CNG Care Ltd | Education | 2023 |
| Cnkk Ltd | Health & social care | 2025 |
| CNR Decoration Ltd | Construction | 2025 |
| Co Sports Events Limited | Arts & recreation | 2023 |
| Coban Decor Limited | Construction | 2009 |
| Coban Holdings Ltd | Financial services | 2026 |
| Cobbolds Classic Cafes Limited | Hospitality | 2025 |
| Coco and Cica Group Ltd | Financial services | 2026 |
| Coco Drip Ltd | Wholesale & retail | 2025 |
| Coco Loves Food Ltd | Hospitality | 2025 |
| Cocoon Media Limited | Wholesale & retail | 2022 |
| Code Yellow Limited | Other services | 2015 |
| Codigo Tech Ltd | Information & communication | 2024 |
| Coffee at 105 Limited | Hospitality | 2023 |
| Coffee C Limited | Real estate | 2022 |
| Coffee Social Ltd | Hospitality | 2019 |
| Coffee to Go (London) Limited | Hospitality | 2010 |
| Cogie Inc Ltd | Real estate | 2020 |
| Cogie Limited | Real estate | 2018 |
| Cogie Services Limited | Health & social care | 2025 |
| Cognilabs Ltd | Information & communication | 2018 |
| Cognition Land and Water Limited | Water & waste | 2005 |
| Coherent Estates Limited | Real estate | 2018 |
| Coje Limited | Health & social care | 2019 |
| Colak Watford Limited | Hospitality | 2015 |
| Cold Freeze Ltd | Professional & scientific | 2025 |
| Cold Storage Logistic UK Ltd | Transport & logistics | 2026 |
| Colin Thompson Design Associates Limited | Professional & scientific | 1979 |
| Colint Limited | Financial services | 2022 |
| Collab House Limited | Professional & scientific | 2018 |
| Collectors House UK Ltd | Wholesale & retail | 2025 |
| Collecttax Ltd | Professional & scientific | 2026 |
| Colne Way Court Management Limited | Real estate | 1987 |
| Colney Group Ltd | Construction | 2024 |
| Cologne Hair Stylist Ltd | Other services | 2018 |
| Colombian Cacao Premium Ltd | Manufacturing | 2024 |
| Colonial Developments Ltd | Extraterritorial | 2006 |
| Colour Solutions Ltd | Construction | 2023 |
| Colstar Investments Ltd | Financial services | 2023 |
| Colterville Limited | Real estate | 1987 |
| Comac Robotics UK Ltd | Manufacturing | 2026 |
| Comak Investments Ltd | Real estate | 2021 |
| Comet Catering Equipment Co. Limited | Manufacturing | 1979 |
| Comfort Aircon Ltd | Construction | 2021 |
| Comfort Housing Developments Limited | Construction | 2019 |
| Comfort Housing Limited | Real estate | 2018 |
| Commercial Construction Group Limited | Administrative & support | 2017 |
| Commercial Hire Ltd | Wholesale & retail | 2021 |
| Community & Environment Project Office Limited | Professional & scientific | 2000 |
| Community AID Limited | Health & social care | 2012 |
| Community Housing Services Ltd | Real estate | 2026 |
| Community Impact Housing Limited | Hospitality | 2023 |
| Community Interpreting and Translation Limited | Administrative & support | 2025 |
| Compass Care Group Limited | Health & social care | 2025 |
| Compass Navigations Ltd | Information & communication | 2026 |
| Compassion in Politics Ltd | Education | 2020 |
| Complete Climate Control Ltd | Administrative & support | 2020 |
| Complete Glass and Glazing Ltd | Extraterritorial | 2021 |
| Complete Quality Services Limited | Professional & scientific | 2019 |
| Complete Scaffold Limited | Construction | 2025 |
| Compound & Growth Partners Ltd | Professional & scientific | 2024 |
| Compusite Limited | Information & communication | 2019 |
| Computer & Laptop Centre Limited | Wholesale & retail | 2010 |
| Comtech International Limited | Information & communication | 1995 |
| Concxpt Studios Ltd | Information & communication | 2023 |
| Condicor Limited | Construction | 2017 |
| Condor Group Holdings Limited | Professional & scientific | 2004 |
| Condor Group Limited | Wholesale & retail | 1939 |
| Condor Homes (Ware) Limited | Real estate | 2021 |
| Condor Homes Limited | Financial services | 2008 |
| Condor Properties (UK) Limited | Real estate | 1999 |
| Conduct Electrical Ltd | Construction | 2020 |
| Conex Trans Ltd | Transport & logistics | 2023 |
| Congo Synthese Ltd | Information & communication | 2015 |
| Coniah Hair and Beauty Ltd | Other services | 2016 |
| Conical Construction Management Ltd | Construction | 2018 |
| Conifer Walk Property Maintenance Ltd | Households | 2025 |
| Conlai Ltd | Information & communication | 2025 |
| Connaught Nail Bar & Spa Limited | Other services | 2025 |
| Connect Atob Ltd | Other services | 2021 |
| Connect Education Trust | Education | 2016 |