| Clemanic Limited | Construction | 2017 |
| Clementine Cleaning Limited | Administrative & support | 2007 |
| Clementine Homes Limited | Real estate | 2021 |
| Clementine Lettings Limited | Real estate | 2021 |
| Clever Frog Limited | Administrative & support | 2018 |
| Cleves Court Management Limited | Households | 1988 |
| Clevy Ltd | Transport & logistics | 2022 |
| Clewborough Consulting Limited | Other services | 2013 |
| Click a Skip Nationwide Limited | Water & waste | 2014 |
| Clickaskip Limited | Extraterritorial | 2015 |
| CLM Studio Ltd | Professional & scientific | 2023 |
| Closh Enterprises Ltd | Financial services | 2024 |
| Cloud 1ST Consulting Ltd | Information & communication | 2017 |
| Cloudmore Ltd | Information & communication | 2006 |
| Cloudveil Limited | Administrative & support | 2017 |
| CM Chef Consultant Ltd | Professional & scientific | 2024 |
| CMC Precision Engineering Limited | Manufacturing | 2004 |
| CMH Projects Limited | Professional & scientific | 2013 |
| CML 1 Limited | Wholesale & retail | 2026 |
| CMM Telecoms Limited | Information & communication | 2017 |
| CMS Business Ltd | Professional & scientific | 2021 |
| Co-Op Motors Limited | Wholesale & retail | 2025 |
| Coalition-Audio Limited | Arts & recreation | 2012 |
| Coan Foods Surrey Limited | Wholesale & retail | 2018 |
| Cobalt Blue Marketing Communications Limited | Wholesale & retail | 1997 |
| Cobault Limited | Information & communication | 1999 |
| Cocatalyst Limited | Professional & scientific | 2008 |
| Code Vibes Ltd | Information & communication | 2004 |
| Codeali Limited | Information & communication | 2014 |
| Codex Theatre Ltd | Arts & recreation | 2025 |
| Cods and Chips Limited | Hospitality | 2024 |
| Coeur Consulting Limited | Professional & scientific | 2024 |
| Coffee G Ltd | Manufacturing | 2026 |
| Cogdel Limited | Education | 2024 |
| Cognitive Talent Ltd | Administrative & support | 2024 |
| Colbert Communications Limited | Professional & scientific | 2008 |
| Colefad Limited | Households | 1986 |
| Coley Management Company Limited | Households | 1989 |
| Colin Jones Solutions Ltd | Real estate | 2004 |
| College Hill Estate Management Limited | Households | 1987 |
| Colne Bar Properties Limited | Real estate | 1997 |
| Colours Limited | Wholesale & retail | 1986 |
| Colourstream Design and Print Limited | Manufacturing | 2005 |
| Coltwood Holdings Limited | Real estate | 1984 |
| Comb Data Limited | Professional & scientific | 2022 |
| Combe Rise Management Company Limited | Households | 1980 |
| Comgas Electrical Ltd | Construction | 2026 |
| Comgas Services UK Ltd | Construction | 2019 |
| Commercial Dispute Resolution Ltd | Professional & scientific | 2012 |
| Commercial Forms Limited | Manufacturing | 1990 |
| Commercial Street (London) Limited | Administrative & support | 2011 |
| Community Networking Limited | Administrative & support | 2021 |
| Compact Cleaning Ltd | Administrative & support | 2019 |
| Compass Place Management Company Limited | Households | 2015 |
| Complete Best Limited | Wholesale & retail | 2016 |
| Complete Mortgages Property Limited | Real estate | 2013 |
| Complete Structures Ltd | Transport & logistics | 2018 |
| Compliance Clarity Limited | Information & communication | 2011 |
| Component Systems Ltd | Wholesale & retail | 2013 |
| Compos Mentis Productions Limited | Information & communication | 2008 |
| Compositeperson Ltd | Professional & scientific | 2023 |
| Compton Financial Services Ltd | Financial services | 2019 |
| Compton Investments Ltd | Real estate | 2015 |
| Compuway Limited | Professional & scientific | 1999 |
| Comunica Ltd | Administrative & support | 2021 |
| Concept Stone Ltd | Construction | 2026 |
| Conco International Ltd | Wholesale & retail | 2020 |
| Conington Limited | Professional & scientific | 1967 |
| Connection (Relationship) Limited | Health & social care | 2012 |
| Connely Roberts Group Ltd | Financial services | 2021 |
| Connexus Networks Ltd | Information & communication | 2005 |
| Connexus Technology Limited | Information & communication | 2008 |
| Conrail (UK) Ltd. | Administrative & support | 2009 |
| Consult 1980 Limited | Professional & scientific | 2020 |
| Consultea Limited | Professional & scientific | 2014 |
| Container Haulage Ltd | Transport & logistics | 2014 |
| Contamination Control Ltd | Wholesale & retail | 2006 |
| Content Rich Consulting Limited | Administrative & support | 2008 |
| Contexis Index C.I.C. | Information & communication | 2018 |
| Context People Consulting Ltd | Professional & scientific | 2026 |
| Cool IT UK Limited | Professional & scientific | 2003 |
| Coombe Park (Charvil) Management Company Limited | Households | 2005 |
| Copper Green Ltd | Construction | 2020 |
| Coppergate Capital Partners Ltd | Financial services | 2026 |
| Coppers Cottages Management Ltd | Professional & scientific | 2002 |
| Coppice Place Residents Limited | Households | 1998 |
| Copse Automotive Ltd | Wholesale & retail | 2019 |
| Copthall House Management Ltd | Administrative & support | 2015 |
| Coralline Ltd | Information & communication | 2011 |
| Corcoran Builders Ltd. | Construction | 2014 |
| Core Business Finance Limited | Financial services | 2025 |
| CORE4FITNESS Ltd | Other services | 2017 |
| Coriander Limited | Manufacturing | 1971 |
| Cormack Tree Care Ltd | Agriculture & fishing | 2004 |
| Cornerstone PM Limited | Construction | 2022 |
| Cornerstone Wills Limited | Professional & scientific | 2003 |
| Cornflower Associates Ltd | Professional & scientific | 2025 |
| Cornish Dreams Property Ltd | Real estate | 2022 |
| Corporate Art Studio Limited | Wholesale & retail | 2024 |
| Corporate Wear Limited | Administrative & support | 2005 |