| Clarent Precision Limited | Manufacturing | 2010 |
| Clargo Construction Limited | Construction | 2026 |
| Claricast Ltd | Information & communication | 2026 |
| Claricy Consulting Ltd | Information & communication | 2024 |
| Clarkall Limited | Financial services | 2025 |
| Class 20 Locomotive Company | Arts & recreation | 2026 |
| Class LB Ltd | Other services | 2021 |
| Classe Parts Limited | Wholesale & retail | 2002 |
| Classic Candle Company Ltd | Manufacturing | 2014 |
| Classic Chassis Services Limited | Manufacturing | 2007 |
| Clavco Limited | Professional & scientific | 2019 |
| Clayacre Management Limited | Households | 1978 |
| Claybourne Property Management Company Limited | Households | 2019 |
| Claymar Metal Products Limited | | 1980 |
| Clean Nation Window Cleaning Limited | Administrative & support | 2013 |
| Clickhealth Limited | Manufacturing | 2011 |
| Cliftylift Limited | Administrative & support | 2026 |
| Clipstone Mews Management Limited | Administrative & support | 2013 |
| Closefield Ltd | Professional & scientific | 2024 |
| Cloud and More IT Limited | Information & communication | 2021 |
| Cloud and More Limited | Other services | 1985 |
| Cloudcoding Limited | Information & communication | 2010 |
| Clover Accounts Limited | Professional & scientific | 2013 |
| Clutter Free Living Ltd | Administrative & support | 2016 |
| CMA Experience Ltd | Arts & recreation | 2025 |
| CMM Holdings Limited | Financial services | 2025 |
| CMV Support Ltd | Transport & logistics | 2024 |
| Coachable Partners Limited | Professional & scientific | 2022 |
| Coastal Concierge Ltd | Other services | 2019 |
| Coco Southend on Sea Ltd | Hospitality | 2018 |
| Codelogic Limited | Information & communication | 2025 |
| Codex Solutions Employee Ownership Trustee Limited | Professional & scientific | 2024 |
| Codex Solutions Limited | Administrative & support | 2007 |
| Codling & Mills Brickwork Contractors Ltd | Construction | 2022 |
| Codling Construction Ltd | Construction | 2026 |
| Cods & Waffles UK Ltd | Hospitality | 2022 |
| Coeus Management Ltd | Information & communication | 2024 |
| Cognition Care Ltd | Health & social care | 2024 |
| Cognitious Ltd | Extraterritorial | 2015 |
| Coin Addiction Ltd | Wholesale & retail | 2020 |
| Cojo Fire & Security Ltd | Construction | 2018 |
| Colcort Jewellery Ltd | Manufacturing | 2013 |
| Colibri Accounting Ltd | Professional & scientific | 2021 |
| Colibri Small Business Academy Ltd | Administrative & support | 2022 |
| Colin Glover Consulting Ltd | Information & communication | 2025 |
| Colin Hoare Accountancy Services Ltd. | Professional & scientific | 2012 |
| Colin Spencer Gleave Ltd | Professional & scientific | 2024 |
| Collection Eleven Limited | Professional & scientific | 2022 |
| Collekit Ltd | Wholesale & retail | 2024 |
| Color GLO MK Ltd | Other services | 2022 |
| Colour LAB Creation Limited | Information & communication | 2013 |
| Colourway Yarns Limited | Wholesale & retail | 2024 |
| Com-Iron Co.,Limited | Financial services | 1928 |
| Combat Evolved Ltd | Information & communication | 2026 |
| Combat Fire Limited | Other services | 2006 |
| Combined Test Solutions Ltd | Manufacturing | 2014 |
| Commercial Property Investment Partnership Limited | Professional & scientific | 2002 |
| Commercial Property Link Limited | Administrative & support | 2020 |
| Community for ALL (C4A) C.I.C. | Education | 2020 |
| Company - Place Limited | Administrative & support | 2018 |
| Complete Construction (Design & Build) Limited | Construction | 2000 |
| Complete Hvac Services Limited | Construction | 2005 |
| Complex Group Ltd | Construction | 2020 |
| Complex Scaffolding Limited | Construction | 2008 |
| Comprehensive Development Services Limited | Real estate | 2012 |
| Compton Investment Property Limited | Real estate | 2021 |
| Compton Land Developments LLP | | 2012 |
| Compton Tankers Limited | Wholesale & retail | 2003 |
| Comptons Developments Limited | Extraterritorial | 2007 |
| Computer Marketing Services Software Limited | Information & communication | 1984 |
| Condor Compliance Ltd | Professional & scientific | 2025 |
| Conduit Networks Limited | Wholesale & retail | 2007 |
| Confident Drivers Ltd | Wholesale & retail | 2017 |
| Connect & Convey Limited | Professional & scientific | 2018 |
| Connect Floor Surrey Limited | Construction | 2020 |
| Connells (MIH) Limited | Extraterritorial | 2008 |
| Connells Estate Agents Limited | Professional & scientific | 2013 |
| Connells Financial Services Limited | Financial services | 1987 |
| Connells Group Limited | Professional & scientific | 2024 |
| Connells Limited | Financial services | 1996 |
| Connells Residential | Financial services | 1980 |
| Connells Survey & Valuation Limited | Professional & scientific | 2000 |
| Connexion Pathways Ltd. | Education | 2025 |
| Conscious Accounting Ltd | Information & communication | 2018 |
| Consulmax Limited | Administrative & support | 2019 |
| Consult MB Ltd | Information & communication | 2003 |
| CONSULTING58 Limited | Professional & scientific | 2015 |
| Continuum Engineering Ltd | Professional & scientific | 2010 |
| Contour Architecture Ltd | Professional & scientific | 2015 |
| Conversations That Count Ltd | Professional & scientific | 2025 |
| Cook the Books Limited | Professional & scientific | 1999 |
| Cooper House Management Company Limited | Households | 1997 |
| Copier Solutions (UK) Limited | Other services | 2002 |
| Coppard Services Limited | Information & communication | 2007 |
| Copper Core Cabling Ltd | Construction | 2022 |
| Copten Coastal Limited | Hospitality | 2025 |
| Copten Limited | Construction | 2017 |
| Corak Limited | Administrative & support | 2010 |
| Coraxis Limited | Wholesale & retail | 2026 |
| Core Create Ltd | Information & communication | 2021 |