| CKW Property Investments Limited | Real estate | 2015 |
| Claire Hindley Limited | Hospitality | 2026 |
| Claire Rider Education Services Ltd | Education | 2025 |
| Claire Shedden Consulting Limited | Professional & scientific | 2012 |
| Clapperboard Construction Ltd | Information & communication | 2016 |
| Claremont Capital Partners Ltd | Construction | 2018 |
| Claremont London Limited | Construction | 2016 |
| Clarence Park Consultants Ltd | Extraterritorial | 2024 |
| Clariti Software Holdings Limited | Financial services | 2024 |
| Clariti Software Limited | Information & communication | 2024 |
| Clark Health Communications Limited | Professional & scientific | 2011 |
| Clarke Acquisition and Rental Limited | Real estate | 2024 |
| Clayhill Constructions Ltd | Construction | 2026 |
| Claymoor Estate Residents Limited | Households | 1980 |
| Clean Air in Cities Ltd | Extraterritorial | 2010 |
| Clean Air in London | Professional & scientific | 2010 |
| Clean Air London Limited | Extraterritorial | 2022 |
| Clean Team 24 Limited | Administrative & support | 2024 |
| CLEAN2GLEAM Limited | Administrative & support | 2007 |
| CLEAN2GLEAM Marine Limited | Administrative & support | 2013 |
| Cleantogleam Products Limited | Wholesale & retail | 2017 |
| Clear Aurora Consulting Ltd | Professional & scientific | 2021 |
| Clear View Mediation & Mentoring Ltd | Professional & scientific | 2023 |
| Clearcut Golf Limited | Arts & recreation | 2021 |
| Clearfocus Limited | Information & communication | 2015 |
| Cleartest Ltd | Professional & scientific | 2020 |
| Clickpop Marketing Ltd | Professional & scientific | 2023 |
| Clifton Heywood Limited | Administrative & support | 2013 |
| Climate Solutions Limited | Construction | 1998 |
| Cloud Bridge Recruitment Limited | Administrative & support | 2024 |
| Cloud Bridge Technologies Limited | Information & communication | 2018 |
| Cloud Scale Technologies Limited | Information & communication | 2024 |
| Cloudable AI Ltd. | Information & communication | 2024 |
| Cloudhuman Ltd | Professional & scientific | 2025 |
| Cloudignyte Ltd | Professional & scientific | 2020 |
| Cloudmt Trading Limited | Wholesale & retail | 2025 |
| CM Advisers Limited | Real estate | 2017 |
| CM Jordan Ltd | Professional & scientific | 2023 |
| Co-Creative Connection Limited | Arts & recreation | 2022 |
| Coaching for Performance Limited | Administrative & support | 2005 |
| Coast Strategy Limited | Administrative & support | 2020 |
| Codecrossing Limited | Information & communication | 2012 |
| Coeus BIO Consulting Limited | Professional & scientific | 2020 |
| Cogendo Limited | Information & communication | 2014 |
| Cogentum Consulting Limited | Professional & scientific | 2018 |
| Cogito Digital Security Ltd | Information & communication | 2024 |
| Cogwork Property Ltd | Real estate | 2021 |
| Cohesive FT UK Limited | Professional & scientific | 2009 |
| Coinstrats Ltd | Information & communication | 2016 |
| Colbur Ltd | Wholesale & retail | 2021 |
| Coldharbour Foods Limited | Wholesale & retail | 2026 |
| Column 8 Ltd | Real estate | 2022 |
| Comfin Ltd | Professional & scientific | 2025 |
| Commercial Property Consultancy (U K) Limited | Real estate | 2010 |
| Commercial Secretariat Limited | Professional & scientific | 1988 |
| Common House Ltd | Professional & scientific | 2026 |
| Complete Design Limited | Professional & scientific | 2008 |
| Completely Independent Distribution Limited | Transport & logistics | 2012 |
| Compton Court Management Company (Slough) Limited | Households | 1976 |
| Concrete Cranes Ltd | Administrative & support | 2021 |
| Condition One Ltd | Administrative & support | 2026 |
| Connect Currencies Ltd | Administrative & support | 2025 |
| Connect for Success Ltd | Professional & scientific | 2015 |
| Connell Properties Ltd | Real estate | 2016 |
| Consilient Capital Ltd | Professional & scientific | 2020 |
| Consilient Partners Ltd | Professional & scientific | 2013 |
| Constantinian Order of ST George Great Britain and Ireland Limited | Other services | 2025 |
| Construction Fixing Systems Holdings Limited | Financial services | 2021 |
| Construction Fixing Systems Ltd | Construction | 1990 |
| Consult W Limited | Professional & scientific | 2018 |
| Contender Films Limited | Administrative & support | 2010 |
| Continuum Wealth (Holdings) Ltd | Financial services | 2020 |
| Continuum Wealth Limited | Financial services | 2010 |
| Cookham Cocktail Club Limited | Arts & recreation | 2021 |
| Coppice Energy Ltd | Professional & scientific | 2023 |
| CORAC3 Limited | Professional & scientific | 2023 |
| Core Aero Ltd | Administrative & support | 2008 |
| Corpcroft Limited | Other services | 2000 |
| Corporate Living Apartments Limited | Hospitality | 2021 |
| Cortec Systems Ltd | Administrative & support | 2022 |
| Corwell (4) Management Limited | Households | 2016 |
| Cosmic Carrot LLP | | 2014 |
| Cosmic Carrot Productions Limited | Information & communication | 2018 |
| Cosmic Kids Brands Limited | Administrative & support | 2020 |
| Cosmic Kids Limited | Extraterritorial | 2021 |
| Cosmic Kids Trading Limited | Education | 2020 |
| Cosydian Limited | Information & communication | 2011 |
| Country Weddings and Events Ltd | Administrative & support | 2019 |
| Courtyard Clinic Marlow Ltd | Real estate | 2026 |
| Coverdrive Consulting Ltd | Professional & scientific | 2010 |
| Cozze Restaurant Limited | Hospitality | 2014 |
| CPA Property Ltd | Administrative & support | 2007 |
| Cracked Stone Ltd | Other services | 2019 |
| Craftclients Ltd | Professional & scientific | 2026 |
| Craufurd Court Residents' Association Limited | Households | 1978 |
| Creative Frameworks Ltd | Extraterritorial | 2011 |
| Creatures United | Administrative & support | 2021 |
| Cresourceful Limited | Professional & scientific | 2024 |
| Crest Secure Automotive Solutions Ltd | Transport & logistics | 2021 |
| Crestwell House Ltd | Financial services | 2025 |