| Clayfield Commercial Limited | Financial services | 2023 |
| CLB Property Limited | Real estate | 2016 |
| Clean Air Public Relations Ltd | Professional & scientific | 2025 |
| Cleanslate Facilities Management Ltd | Administrative & support | 2025 |
| Clear Blue Developments Ltd | Construction | 2020 |
| Clearer Retirement Ltd | Professional & scientific | 2017 |
| Clearline Care Services Limited | Administrative & support | 2022 |
| Clearline Healthcare Limited | Administrative & support | 2019 |
| Clements Harris Communications Strategies Ltd | Professional & scientific | 2018 |
| Cleveland Renewables Limited | Professional & scientific | 2015 |
| Clever Events & Productions Limited | Administrative & support | 2024 |
| Clever One Holdings Limited | Financial services | 2024 |
| Click Audio Post Production Ltd | Information & communication | 2012 |
| Click News and Media Limited | Professional & scientific | 2019 |
| Click Viral Ltd | Administrative & support | 2026 |
| Cliff Cottages Management Company Limited | Real estate | 2017 |
| Cliffe Road Limited | Real estate | 2022 |
| Clifton HR Ltd | Professional & scientific | 2011 |
| Clinical Aesthetics by Lara Ltd | Health & social care | 2024 |
| Clipper Group Limited | Professional & scientific | 2014 |
| Clockhouse Studios Limited | Financial services | 2026 |
| Clockwork Content Ltd | Professional & scientific | 2018 |
| Cloud Cadence Ltd | Information & communication | 2023 |
| Cloud Contracts 365 Ltd | Information & communication | 2023 |
| Cloud Taken Ltd | Information & communication | 2017 |
| Cloud Tales Ltd | Information & communication | 2024 |
| Cloud Video Limited | Information & communication | 2011 |
| CLOUD27 Ltd | Professional & scientific | 2013 |
| Cloudline Tech Ltd | Wholesale & retail | 2025 |
| Cloudy Byte Solutions Ltd | Information & communication | 2023 |
| CLR Swim Schools LLP | | 2012 |
| CLU Infotech Ltd | Information & communication | 2023 |
| Clubguard Ltd | Information & communication | 2026 |
| Clubladdr Ltd | Information & communication | 2025 |
| Clubs Quantum Ltd | Hospitality | 2023 |
| Clubs Quantum TW Property Ltd | Hospitality | 2023 |
| Clun Woodlands Limited | Agriculture & fishing | 1998 |
| Clutton Associates Ltd | Professional & scientific | 2023 |
| Clyde Cloud Consulting Ltd | Information & communication | 2024 |
| CMC Financial Ltd | Financial services | 2025 |
| CMT Property Management Limited | Real estate | 2022 |
| CN Construction Ltd | Construction | 2019 |
| CNC Creative Construction Limited | Construction | 2022 |
| CNC Laminates Limited | Professional & scientific | 2002 |
| CNC Wealth Management Limited | Real estate | 2024 |
| Cncl Ltd | Construction | 2018 |
| CO2NVERSIONS Limited | Information & communication | 2022 |
| Coach Ltd | Administrative & support | 2008 |
| Coach Report AI Ltd | Information & communication | 2026 |
| Coates Media Ltd | Information & communication | 2021 |
| Coblands Landscapes Limited | Administrative & support | 1973 |
| Cobra Cyber Security Ltd | Information & communication | 2016 |
| Coco Retro Limited | Hospitality | 2016 |
| Code Dogs Ltd | Information & communication | 2023 |
| Code Replete Ltd | Information & communication | 2017 |
| Codes Green Ltd | Information & communication | 2019 |
| Codingtank Limited | Information & communication | 2014 |
| Codreanuconstruction Limited | Construction | 2018 |
| Cog-Ed Ltd | Professional & scientific | 2015 |
| Cog-Ed Psychology Ltd | Professional & scientific | 2021 |
| Cogeleven Limited | Health & social care | 2023 |
| COGS4KIDS Limited | Education | 2019 |
| Cohesion Consulting Ltd | Information & communication | 2021 |
| Colbek Limited | Real estate | 2017 |
| Colden Farming Limited | Agriculture & fishing | 1997 |
| Coldframe Consulting Limited | Professional & scientific | 2016 |
| Coldman Estates Limited | Construction | 2017 |
| Colin Elves Limited | Information & communication | 2014 |
| Colin Lewis Building Limited | Construction | 2007 |
| Collaboration Wave Ltd | Professional & scientific | 2025 |
| Collaborative Food Ventures Limited | Professional & scientific | 2015 |
| Colley Raine & Associates Ltd | Extraterritorial | 2021 |
| Collibrook Heating Services Limited | Construction | 2017 |
| Colliers International Capital Markets UK LLP | | 2014 |
| Colliers International Central London UK LLP | | 2014 |
| Comb Place Management Limited | Households | 1999 |
| Combi World Limited | Manufacturing | 2015 |
| Comentco Ltd | Professional & scientific | 2025 |
| Coming UP for Air (CJB) Limited | Administrative & support | 1987 |
| Coming UP for Air (DJC) Limited | Administrative & support | 2005 |
| Coming UP for Air LLP | | 2003 |
| Commercehive Ltd | Wholesale & retail | 2025 |
| Communications Holding Company Limited | Wholesale & retail | 2020 |
| Community Golfcentral Limited | Wholesale & retail | 2020 |
| Community Hub, Sports, & Wellbeing CIC | Health & social care | 2026 |
| Community Operated Projects and Events (Cope) Limited | Professional & scientific | 2026 |
| Company Compliance Ltd | Extraterritorial | 2023 |
| Compare Builders Merchants Ltd | Information & communication | 2020 |
| Compass Financial Recovery & Insolvency Limited | Professional & scientific | 2005 |
| Compass Life Coaching Ltd | Education | 2025 |
| Complete Denture Care Limited | Health & social care | 2009 |
| Compliance Logbook Ltd | Wholesale & retail | 2025 |
| Compliance.Finance Limited | Professional & scientific | 2017 |
| Computer Gurus AI Limited | Information & communication | 2026 |
| Computer Gurus Limited | Other services | 2004 |
| Concept Builders South East Ltd | Other services | 2018 |
| Concept by Hannah Ltd | Manufacturing | 2023 |
| Concept Coatings Specialist Ltd | Construction | 2020 |
| Concept Plastic Surgery Ltd | Health & social care | 2013 |
| Conceptual Engineering Inc Ltd | Education | 2022 |