| Business Intelligence Consulting Ltd | Information & communication | 2003 |
| Business Technology Consultants Ltd | Construction | 1984 |
| Butterworth Laboratories Limited | Professional & scientific | 1974 |
| Buzz-Erk Limited | Information & communication | 2003 |
| BWI Systems Limited | Information & communication | 2003 |
| Byfleet Investments Limited | Real estate | 2007 |
| Byron Hill Management Limited | Real estate | 2002 |
| Bzdollis Ltd | Real estate | 2016 |
| C & G Property Partnership Ltd | Real estate | 2025 |
| C & M Distributors (Impex) Limited | Wholesale & retail | 1981 |
| C F Ventures | | 2004 |
| C G Marketing Insight Limited | Administrative & support | 2007 |
| C M E Trading Limited | Transport & logistics | 1987 |
| C Mcgarvey Properties Limited | Real estate | 2001 |
| C O'Shea Ltd | Construction | 2003 |
| C. & P. Kyriacou Limited | Real estate | 1971 |
| C. H. LIM & Associates Ltd | Health & social care | 1999 |
| C.And G.Austin Limited | Construction | 1969 |
| C.B.T. Electrical Limited | Construction | 1997 |
| C.C. TV Direct (London) Limited | | 1998 |
| C.Cripps & SON Limited | Manufacturing | 1959 |
| C.E Rail Limited | Transport & logistics | 2014 |
| C.H.S. Holdings Limited | | 1985 |
| C.J. Burgess and SON Limited | Extraterritorial | 2005 |
| C.T.A. Economic & Export Analysts Limited | Professional & scientific | 1980 |
| Cable Adnet Communications Limited | Information & communication | 2003 |
| Cables Fans & Fittings Limited | Wholesale & retail | 1978 |
| Cadcons Limited | Professional & scientific | 2003 |
| Cadman DBP Limited | Professional & scientific | 1921 |
| Caerleon Design Services Limited | Professional & scientific | 2007 |
| Caffe' Mimmo Bar Limited | Hospitality | 2004 |
| Calculus Research Limited | Professional & scientific | 1994 |
| Calculus Software Limited | Information & communication | 1994 |
| Calderwood Agencies Ltd | Professional & scientific | 1995 |
| Calmgrade Limited | Real estate | 2000 |
| Calos Funeral Directors Limited | Other services | 2003 |
| Calvary Design Ltd | Information & communication | 2004 |
| CAM Resources Ltd | Professional & scientific | 2020 |
| Cambian Foods Limited | Manufacturing | 1988 |
| Cambridge Soundworks U.K. Limited | | 1990 |
| Camfreight Distribution Limited | | 1986 |
| Campania Foods Limited | Wholesale & retail | 2004 |
| Canons Association Limited | Wholesale & retail | 1985 |
| Canons Enterprises Limited | Arts & recreation | 1992 |
| Canopus Global Limited | Professional & scientific | 2011 |
| Canpar Warehousing and Transport Limited | | 1979 |
| Canterbury Brewing Company Limited | Extraterritorial | 2002 |
| Capatulo Limited | Information & communication | 2025 |
| Cape Scaffolding Limited | Professional & scientific | 1975 |
| Capital Investment and Property Management LLP | | 2023 |
| Capital Lock & Safe Company Limited | Wholesale & retail | 1965 |
| Capital Property Consulting Limited | Real estate | 2023 |
| Capital Vehicle Maintenance Limited | Wholesale & retail | 1995 |
| Capto Cloud Limited | Information & communication | 2025 |
| Capto Limited | Information & communication | 2026 |
| Car Audio & Security Limited | Wholesale & retail | 1999 |
| Car Park Ltd | Other services | 2019 |
| Car Valeting Details Ltd | Administrative & support | 2024 |
| Cara Global Sales & Marketing Limited | Professional & scientific | 2025 |
| Cara Personnel Employment Limited | Administrative & support | 1987 |
| Carbonel Ltd | Professional & scientific | 2019 |
| Cardboard Tubes Limited | Professional & scientific | 2007 |
| Cardiology Diagnostics Limited | Health & social care | 2007 |
| Cards Direct (Herts) Limited | Wholesale & retail | 2003 |
| Carers Trust Hillingdon and Ealing | Health & social care | 2000 |
| Cargo Express International Limited | Transport & logistics | 1997 |
| Caring Consultancy Limited | Health & social care | 2005 |
| Carl Irwin Ltd | Health & social care | 2006 |
| Carmichael Components Limited | Wholesale & retail | 1985 |
| Caroline Paris Ltd | Information & communication | 2024 |
| Carpet - Rite Limited | Wholesale & retail | 2004 |
| Carpet and Luggage Express Ltd | Wholesale & retail | 2022 |
| Carpet Outline Limited | Wholesale & retail | 1982 |
| Carpetstyle Limited | Wholesale & retail | 1990 |
| Carrigart Construction Ltd | Construction | 2014 |
| Carrington Brothers Limited | Construction | 2004 |
| Cartage Holdings Limited | Professional & scientific | 1996 |
| Carterhatch Management Limited | Households | 1991 |
| Casa Cara Ltd | Real estate | 2007 |
| Casey Creative Limited | Arts & recreation | 2004 |
| Cast & Crew Supply Limited | Administrative & support | 2025 |
| Castlebar Freehold Limited | Real estate | 1999 |
| Castlebrook Enterprises Limited | Administrative & support | 1997 |
| Castleclose Properties Ltd | Real estate | 2025 |
| Castlemist Finances Limited | Construction | 1997 |
| Castnet Limited | Information & communication | 2002 |
| Castrol Holdings Americas Limited | Financial services | 2020 |
| Castrol Holdings International Limited | Financial services | 2020 |
| Castrol Offshore Limited | Professional & scientific | 1994 |
| Cat Accounts Ltd | Professional & scientific | 2011 |
| Cathay Foods Limited | Extraterritorial | 2006 |
| Catherine Jones Limited | Wholesale & retail | 1988 |
| Catherine Roberts Limited | | 1994 |
| Cavendish Morgan Limited | Manufacturing | 2026 |
| Cayan Brothers Properties Limited | Real estate | 2021 |
| CBJ International Limited | Wholesale & retail | 2001 |
| Cdata Consultancy Limited | Information & communication | 2007 |
| CDV-2, Ltd. | Financial services | 2002 |
| CEA Architects Limited | Professional & scientific | 2018 |
| Cecil E. Watts Limited | Real estate | 1958 |