| Colbair Services Limited | Manufacturing | 2003 |
| Colestone Investments Limited | Professional & scientific | 2013 |
| Colin Tart Holdings Ltd | Financial services | 2024 |
| Colinade Associates Limited | Information & communication | 1996 |
| Collinsons Limited | Real estate | 1997 |
| Coltan Limited | Information & communication | 2006 |
| Comfort Cooling Installations Limited | Energy | 2007 |
| Commotions Limited | Wholesale & retail | 2001 |
| Complete Integrated Services Limited | Information & communication | 1994 |
| Computacenter PLC | Professional & scientific | 1995 |
| Concave Ltd | Professional & scientific | 2006 |
| Condense Technology | | 1997 |
| Confluence Trading and Investment Ltd | Information & communication | 2015 |
| Connaught Green (Anfield) Management Company Limited | Households | 2008 |
| Connect Plus (M25) Issuer PLC | Financial services | 2018 |
| Connecting People Limited | Transport & logistics | 1997 |
| Connections Sanctuary Limited | Administrative & support | 2023 |
| Connor Construction Limited | Construction | 1983 |
| Conquer Hospitality Ltd | Hospitality | 2021 |
| Consolidated Corporation Limited | Construction | 1994 |
| Constellation Communications Limited | Information & communication | 2000 |
| Construction & Shopfitting Limited | Construction | 1998 |
| Consultation Support Systems Limited | Professional & scientific | 1997 |
| Consulting Connections Limited | Professional & scientific | 2005 |
| Contract Cover Limited | Information & communication | 2003 |
| Control Gear Distributors Ltd. | Extraterritorial | 1987 |
| Cool Cars 'N' Parts Ltd. | Professional & scientific | 1990 |
| Cool Luxury Designs Limited | Other services | 2002 |
| Cool World UK Limited | Professional & scientific | 2001 |
| Coombs Direct Limited | Construction | 1999 |
| Coover Ltd | Real estate | 2019 |
| Cordoba Management Company Limited | Construction | 2006 |
| Cornerstones Pre-School Limited | Education | 2003 |
| Cornhill Residents Association Limited | Households | 2003 |
| Corporate Governance Services Limited | Professional & scientific | 2006 |
| Cortoor Construction Limited | Construction | 2005 |
| Cosmex (Trading) Limited | | 1986 |
| Cosmos Systems and Programmers Limited | Information & communication | 1970 |
| Costco Limited | Real estate | 1992 |
| Cotetarn Limited | Households | 1978 |
| Count on ME Tutor Ltd | Education | 2025 |
| Countdown Technology Limited | Professional & scientific | 2000 |
| Country House Weddings Limited | Administrative & support | 1998 |
| Country Properties | | 1993 |
| Countryside SKI & Climb Limited | Wholesale & retail | 1994 |
| Courte Paille Properties Limited | Hospitality | 1999 |
| Courtney Smith Group Limited | Administrative & support | 2003 |
| Courtney Smith Holdings Limited | Extraterritorial | 2007 |
| Covmo Coventry Motors Limited | Wholesale & retail | 2005 |
| Covmo Limited | Wholesale & retail | 2005 |
| CP Partnership Limited | Professional & scientific | 2013 |
| Cpig Limited Partnership | | 2005 |
| CPM Business Consultancy Limited | Professional & scientific | 1997 |
| CPS Flooring Limited | Construction | 2002 |
| Craig-Y-Mor Management Company (Aberdyfi) Limited | Real estate | 1998 |
| Cranmore Digital Consulting Limited | Professional & scientific | 2007 |
| Crazy Cuts (London) Limited | Other services | 2010 |
| Creagus Installations Limited | Construction | 2004 |
| Crest Ultrasonics Europe Limited | Manufacturing | 1993 |
| Crestbloomlamps Ltd | Wholesale & retail | 2025 |
| Crispin Green Film Editing Limited | Information & communication | 2002 |
| CRK Properties Ltd. | Real estate | 2003 |
| CRM E-Services Ltd | Information & communication | 2004 |
| Crnn Properties Ltd | Real estate | 2023 |
| Crookell-Slade Limited | Education | 2003 |
| Croziers Consultant Surveyors Limited | Professional & scientific | 2000 |
| CRS Structures Ltd | Construction | 1998 |
| Crystek Consulting Limited | Professional & scientific | 2007 |
| CS. Construction and Groundworks Ltd | Construction | 2025 |
| CSS Media Limited | Professional & scientific | 2021 |
| CT Coachworks Ltd | Wholesale & retail | 2023 |
| CTS Recruitment Limited | Financial services | 1995 |
| Cuffley Builders Limited | Construction | 2006 |
| Cula Limited | Professional & scientific | 1989 |
| Curated Holdings Ltd | Financial services | 2026 |
| Current Knot Ltd | Wholesale & retail | 2025 |
| Curtis Associates Limited | Professional & scientific | 2003 |
| Curtis Medical Investments (Letchworth) Limited | Real estate | 2001 |
| Curtis Trust Limited | Real estate | 1936 |
| Curve Design Limited | Professional & scientific | 1998 |
| Customised Management Services Ltd | Professional & scientific | 2001 |
| Cyberdog UK Limited | Wholesale & retail | 2003 |
| D B Cleaning & Maintenance Services Limited | Administrative & support | 2003 |
| D Bacon & SON Building Contractors Ltd | Construction | 2007 |
| D F Keane Building Services Limited | Construction | 1999 |
| D H B Networks Limited | Information & communication | 1998 |
| D I Smith GAS Plumbing and Heating Limited | Construction | 2001 |
| D J Clarke Ltd | Professional & scientific | 2007 |
| D M T Associates Limited | Professional & scientific | 1996 |
| D S Water Softeners Ltd | Construction | 2006 |
| D. Fitzgerald Builders Limited | Construction | 2007 |
| D. Weatherhead (Estates) Limited | Financial services | 1945 |
| D. Weatherhead Limited | Construction | 1981 |
| D.B. Rees (Builders) Limited | Construction | 1968 |
| D.B. Rees (DRY Lining) Limited | Construction | 1977 |
| D.C.P. Decor Limited | Construction | 1998 |
| D.N.J. Ltd. | Manufacturing | 1994 |
| D.S. Brickwork & Groundwork Limited | Construction | 2003 |
| D.T.T. Consultancy Limited | Professional & scientific | 2005 |
| Daar Consultancy Limited | Information & communication | 2005 |