| CJV Music & Events Limited | Information & communication | 2023 |
| CJV Properties Limited | Real estate | 2000 |
| CK Performance Academy Ltd. | Education | 2020 |
| Cksp Consulting Ltd | Professional & scientific | 2015 |
| CLA Heating & Plumbing Ltd | Construction | 2023 |
| Clare Llewellyn Ltd | Professional & scientific | 2023 |
| Clare Moll Limited | Real estate | 2011 |
| Clarity Financial Training Ltd | Education | 2018 |
| Clark Farrow Ltd | Construction | 2020 |
| Clarvis Limited | Real estate | 2026 |
| Classic Gardens Limited | Administrative & support | 2014 |
| Classic Mini Spares Limited | Extraterritorial | 1999 |
| Claudeworx Ltd | Information & communication | 2026 |
| Claus Marsh Ltd | Manufacturing | 2011 |
| Clay Investment Limited | Real estate | 2021 |
| Clean Management Ltd | Administrative & support | 2025 |
| Cleveland Production Ltd | Administrative & support | 2014 |
| Clever Bean Accounting Limited | Professional & scientific | 2012 |
| Clever Infomedia Limited | Information & communication | 2019 |
| Cliffhanger Limited | Administrative & support | 2013 |
| Clifton Third Ltd | Arts & recreation | 2022 |
| Climate Force Ltd | Construction | 2017 |
| Clinic Hub 2 Limited | Other services | 2025 |
| Clinical Dynamics Ltd | Administrative & support | 2019 |
| Clkd Capital Limited | Other services | 2025 |
| Clkdon Limited | Other services | 2024 |
| Cloud 9 (Brighton) Limited | Manufacturing | 2010 |
| Cloud Cafe Ltd | Hospitality | 2013 |
| Cloudreap Ltd | Information & communication | 2025 |
| Club Street Studios Ltd | Administrative & support | 2017 |
| Cluster Cabaret Limited | Other services | 2026 |
| CMI Live LLP | | 2012 |
| CMI Touring LLP | | 2016 |
| Cmmttd Limited | Manufacturing | 2019 |
| CMT Construction and Brokerage Ltd | Administrative & support | 2016 |
| Cnak Advisory Ltd | Administrative & support | 2025 |
| Cockfosters Delicatessen Limited | Wholesale & retail | 2011 |
| Coco's Cauldron Ltd | Wholesale & retail | 2025 |
| Code Vanilla Limited | Information & communication | 2010 |
| Codina Investments Limited | Real estate | 2025 |
| COL Couriers Limited | Transport & logistics | 2026 |
| Cola Creative Ltd | Information & communication | 2022 |
| Coles Basement Systems Limited | Construction | 2012 |
| Coley Limited | Water & waste | 1994 |
| Colin Chick Consultancy Limited | Information & communication | 2016 |
| Coltrane Consulting Ltd | Professional & scientific | 2010 |
| Comet HR Limited | Hospitality | 2004 |
| Comfysmiles Ltd | Health & social care | 2026 |
| Community Employment Empowerment & Training Ltd | Administrative & support | 2024 |
| Community Empowerment Employment & Training C.I.C. | Administrative & support | 2020 |
| Competition Silencers (International) Limited | Extraterritorial | 1983 |
| Competitive Solutions Limited | Professional & scientific | 2004 |
| Complex Roofing Solutions Limited | Construction | 2021 |
| Computer Communications U.K. Ltd. | Information & communication | 1992 |
| Computonic Limited | Information & communication | 2005 |
| Concept Design 95 Ltd | Construction | 1996 |
| Concept Stills and Motion Ltd | Wholesale & retail | 2011 |
| Concept Street Food Limited | Wholesale & retail | 2025 |
| Conceptual Group Ltd | Construction | 2024 |
| Conceptual Images Limited | Professional & scientific | 2007 |
| Concierge Services Limited | Administrative & support | 2024 |
| Concorde Express Ltd | Professional & scientific | 2015 |
| Concordia AC Limited | Professional & scientific | 2026 |
| Conex Europe Limited | Administrative & support | 2009 |
| Confrontwork Ltd | Real estate | 2025 |
| Conhen Limited | Real estate | 1997 |
| Connect Trading Ltd | Professional & scientific | 2025 |
| Connections Exhibitions Limited | Professional & scientific | 2005 |
| Connell Roberts Holdings Ltd | Real estate | 2025 |
| Connifers Care Holdings Co Ltd | Financial services | 2026 |
| Connifers Care Limited | Health & social care | 2003 |
| Connifers Properties Limited | Real estate | 2026 |
| Consilium Verification Ltd | Construction | 2026 |
| Constantin-Tiberiu Transport Limited | Transport & logistics | 2017 |
| Constructech Limited | Other services | 2002 |
| Construction & Built Environment Marketing Network Limited | Professional & scientific | 2011 |
| Content Head Limited | Information & communication | 2026 |
| Contract 555 Ltd | Construction | 2024 |
| Coolbury 44 Ltd | Administrative & support | 2024 |
| Coolhurst Care Limited | Health & social care | 2026 |
| Cooper Hathaway Limited | Professional & scientific | 2002 |
| Core Insulations Limited | Construction | 2025 |
| Cornall Music Limited | Arts & recreation | 2012 |
| Corporate Budgeting & Forecasting Solutions Ltd. | Information & communication | 2012 |
| Corporate Property Agency Limited | Real estate | 2021 |
| Corr's Performance Cars Ltd | Wholesale & retail | 2020 |
| Corsair Global Limited | Professional & scientific | 2023 |
| Corsair Group Ltd | Professional & scientific | 2019 |
| Corsair Holdings Limited | Professional & scientific | 2007 |
| Corsair Lifestyle Ltd | Other services | 2016 |
| Cosmea Leonto Ltd | Education | 2015 |
| Cosmo Platers (London) Limited | Wholesale & retail | 1988 |
| Costa Interactive Limited | Information & communication | 2021 |
| Cotswold Restaurant Group Ltd | Hospitality | 2019 |
| Cottingham Road Development Limited | Construction | 2019 |
| Country Boys Music Limited | Information & communication | 2025 |
| Courtco Limited | Administrative & support | 2014 |
| Courtney Jane Ltd | Professional & scientific | 2016 |
| Cousin Food Centre Ltd | Extraterritorial | 2024 |
| Cousins Holdings Limited | Professional & scientific | 1964 |