| Complete Risk Management Solutions Ltd | Financial services | 2025 |
| Complete Solar Management Ltd | Construction | 2018 |
| Complete Tyre Management Ltd | Wholesale & retail | 2011 |
| Complex Property Ltd | Real estate | 2022 |
| Compliance & Management Solutions Limited | Professional & scientific | 2023 |
| Compliance Assistant Limited | Administrative & support | 2021 |
| Compliance Financial Limited | Professional & scientific | 2009 |
| Component Solutions Manufacturing Ltd | Manufacturing | 2023 |
| Compose Code Limited | Information & communication | 2024 |
| Compounding Equity Investment UK Ltd | Financial services | 2022 |
| Compsych Limited | Professional & scientific | 2010 |
| Con's Green & Clean Services Ltd | Administrative & support | 2025 |
| Conair Ducting Ltd | Construction | 2023 |
| Concept Original Ltd | Information & communication | 2022 |
| Concept Tiling Limited | Administrative & support | 2010 |
| Concreations Limited | Manufacturing | 2006 |
| Conex International Limited | Information & communication | 2015 |
| Confluency Limited | Professional & scientific | 2017 |
| Confused Indian Girl Ltd | Professional & scientific | 2024 |
| Conimp Ltd | Construction | 2022 |
| Conkryl Resin Flooring Solutions and Consultancy Limited | Construction | 2026 |
| Connaughts Limited | Construction | 2004 |
| Connaughts Site Investigation Ltd | Construction | 2009 |
| Connect Music Therapy Ltd | Administrative & support | 2019 |
| Connect Today Ltd | Wholesale & retail | 2022 |
| Connection Construction Limited | Construction | 2016 |
| Connection Investments Limited | Real estate | 2013 |
| Connection Property Solutions Ltd | Real estate | 2021 |
| Connective Carpentry and Building Limited | Construction | 2011 |
| Connetopia Food Ltd | Manufacturing | 2024 |
| Connor Ferris Architects Ltd | Professional & scientific | 2026 |
| Connor's Housing Solutions Limited | Real estate | 2025 |
| Conquer Accountancy Ltd | Professional & scientific | 2022 |
| Consolidated Taverns Limited | Hospitality | 2015 |
| Constable Gardens (Residents) Management Company Limited | Households | 2023 |
| Constanta Building Services Ltd | Construction | 2024 |
| Construction by Design Limited | Construction | 2020 |
| Construction Gold Ltd | Administrative & support | 2025 |
| Construction Graphics Solutions Limited | Professional & scientific | 2021 |
| Construction Inc Ltd | Construction | 2022 |
| Construction Materials Matrix Limited | Information & communication | 2025 |
| Construction World Ltd | Construction | 2019 |
| Constructive Films Ltd | Extraterritorial | 2024 |
| Constructive Music Ltd | Arts & recreation | 2020 |
| Consult Inline Limited | Professional & scientific | 2003 |
| Consult Plus (UK) Ltd | Professional & scientific | 2014 |
| Consult PS Limited | Administrative & support | 2024 |
| Consult PT Ltd | Information & communication | 2017 |
| CONSULT4IT Limited | Information & communication | 2016 |
| Consulting Group (Southern) Limited | Financial services | 2017 |
| Consultwheel Ltd | Information & communication | 2018 |
| Contenter Limited | Information & communication | 2014 |
| Contracts London Limited | Administrative & support | 2021 |
| Control-X Limited | Information & communication | 1998 |
| Convivi Limited | Financial services | 2023 |
| Cooke Design Limited | Professional & scientific | 2008 |
| Cooke Limited | Financial services | 2016 |
| Cooke Sosa International Limited | Financial services | 2012 |
| Cookesmith Ltd | Professional & scientific | 2016 |
| Cookies and Koalas Ltd | Wholesale & retail | 2023 |
| Cookiesis Limited | Health & social care | 2023 |
| Cool to BE Kind Limited | Health & social care | 2021 |
| Cooler Security Limited | Administrative & support | 2012 |
| Coolzone Air Conditioning Group Ltd | Energy | 2023 |
| Coombe Rentals Limited | Administrative & support | 2013 |
| Coombs & Lannon Ltd | Professional & scientific | 2026 |
| Coopae Ltd | Wholesale & retail | 2024 |
| Cooper Contracting Limited | Construction | 2009 |
| Cooper Training & Recruitment Ltd | Administrative & support | 2001 |
| Coopers Boreham Ltd | Hospitality | 2024 |
| Coopers Sandwich Ltd | Hospitality | 2021 |
| COOPERSK9S Ltd | Education | 2024 |
| Copper Click Ltd | Professional & scientific | 2021 |
| Coppercraft Electrical Ltd | Manufacturing | 2026 |
| Copperfield (North Melbourne) Management Company Limited | Households | 1983 |
| Coppins Marr Limited | Professional & scientific | 2014 |
| COR Blocks Ltd | Information & communication | 2022 |
| Coral Stores Limited | Wholesale & retail | 2013 |
| Corduroy Submarine Limited | Wholesale & retail | 2022 |
| Core Audio Solutions Ltd | Administrative & support | 2025 |
| Core Handyman Services Ltd | Construction | 2024 |
| Core Investments (Essex) Limited | Real estate | 2021 |
| Core Property Limited | Real estate | 2002 |
| Core Skills Education Ltd | Education | 2024 |
| Coremo Ocmea Limited | Extraterritorial | 1996 |
| Corillion Consult Ltd | Professional & scientific | 2022 |
| Corinthian Ceramics Holdings Limited | Financial services | 2018 |
| Corinthian Ceramics Limited | Construction | 2006 |
| Corinthian Square Limited | Real estate | 2005 |
| Cormark Limited | Manufacturing | 2008 |
| Cornelius Management Limited | Professional & scientific | 2021 |
| Cornelius Wealth Management Ltd | Professional & scientific | 2023 |
| Corner House Leisure Ltd | Hospitality | 2021 |
| Cornershop Chelmsford Limited | Wholesale & retail | 2024 |
| Cornerstone Investments Canada Limited | Real estate | 2006 |
| Cornwall Organic Produce Ltd | Wholesale & retail | 2023 |
| Corporate Plus Umbrella Limited | Administrative & support | 2016 |
| Corpus Capital Management Ltd | Financial services | 2024 |
| Corrmarine Ltd | Transport & logistics | 2017 |
| Cortex Crew Ltd | Administrative & support | 2017 |