| Colne Yacht Club Limited | Real estate | 1912 |
| Colourful Creations Limited | Administrative & support | 1999 |
| Colourful Nails Limited | Other services | 2020 |
| Colourtransfusion | | 2000 |
| Colt Security Systems Limited | Construction | 1992 |
| Columnco Ltd | Wholesale & retail | 2023 |
| Colvanbridge Limited | Transport & logistics | 1978 |
| Comfort Cars Ltd. | Transport & logistics | 2005 |
| Comfort N Style Ltd | Wholesale & retail | 2025 |
| Comfort Operative Ltd | Other services | 2017 |
| Comfort With LDA Ltd | Wholesale & retail | 2026 |
| Commercefox Limited | Wholesale & retail | 2025 |
| Commercial Glass Limited | Wholesale & retail | 2007 |
| Commercial Vehicle Locks Limited | Wholesale & retail | 2009 |
| Commercial Window Cleaning London Ltd | Administrative & support | 2008 |
| Commodity Risk Consultants Limited | Professional & scientific | 2015 |
| Communication Network Solutions Limited | Information & communication | 2005 |
| Compact Storage Equipment Limited | Other services | 1995 |
| Complete Checking Services Ltd | Other services | 2025 |
| Complete Decorum Limited | Construction | 2001 |
| Complete Electrical Services (UK) Limited | Construction | 2005 |
| Complete Plumbing and Heating Limited | Wholesale & retail | 2002 |
| Complete Security Applications Limited | Administrative & support | 1997 |
| Complete Upvc Window Systems Limited. | Professional & scientific | 1988 |
| Compound Media Limited | Administrative & support | 2006 |
| Compstad Consultancy Limited | Professional & scientific | 2026 |
| Compucounts Limited | Extraterritorial | 1994 |
| Computer Generated Solutions UK Ltd | Information & communication | 2019 |
| Computer USE | | 1993 |
| Computerworld.Uk.Com Limited | Information & communication | 2002 |
| Comtrada Ltd | Wholesale & retail | 1999 |
| Comtrust Solutions Limited | Information & communication | 1997 |
| Concept (UK) Building Systems Limited | Other services | 1997 |
| Concept Conservatories Ltd | Construction | 2009 |
| Concept Doors Limited | Manufacturing | 2003 |
| Concept Fitness Essex Limited | Arts & recreation | 2007 |
| Concurrere Punctum Ltd | Other services | 2013 |
| Confabulate Limited | Information & communication | 2005 |
| Confidence Services Limited | Construction | 2018 |
| Confidential Accounting Management Ltd. | Professional & scientific | 2004 |
| Confusion Ltd | Financial services | 2003 |
| Conga Fitness Ltd | Manufacturing | 2021 |
| Conquest Properties Ltd | Real estate | 2014 |
| Consensus Service Management Ltd | Professional & scientific | 2007 |
| Consolidated Services Group Limited | Extraterritorial | 2009 |
| Consstar Ltd | Construction | 2024 |
| Construction Products Solutions Ltd | Wholesale & retail | 2003 |
| Consult a Penguin Ltd | Administrative & support | 2017 |
| Consultancy Support Services Ltd | Professional & scientific | 2019 |
| Consultants of Foreign Education (Cofe) Ltd | Education | 2022 |
| Contact First Ltd | Wholesale & retail | 2024 |
| Container Road Limited | | 1984 |
| Continental Ice Cream Foods Limited | Manufacturing | 1984 |
| Contract Management Professionals Ltd | Professional & scientific | 2017 |
| Contractor Core Payroll Ltd | Administrative & support | 2025 |
| Control Investment Limited | Real estate | 1991 |
| Conveyance Finder Ltd | Wholesale & retail | 2025 |
| Cookies Empire Limited | Wholesale & retail | 2019 |
| Coolime Limited | Hospitality | 2017 |
| Coonch Ltd | Information & communication | 2021 |
| Cooper Hirst Limited | Construction | 1989 |
| Cooper Paul Resources Limited | Professional & scientific | 1999 |
| Coopers Coborn Allweather Pitch Ltd. | Arts & recreation | 1993 |
| Coote Properties Limited | Real estate | 1995 |
| Copper Cloud Consulting Limited | Information & communication | 2015 |
| Copybest (Essex) Limited | Wholesale & retail | 1991 |
| Copyfax (Business Services) Limited | Professional & scientific | 1991 |
| Core Heating and Energy Limited | Construction | 2026 |
| Core Maintenance Services (London) Limited | Construction | 2020 |
| Core Translation Ltd | Professional & scientific | 2025 |
| Corecomputer Ltd | Wholesale & retail | 2025 |
| Corelane Construction Ltd | Construction | 2026 |
| Coremetrics Ltd | Transport & logistics | 2025 |
| Coris Properties Limited | Real estate | 1953 |
| Cornier Solutions Ltd | Health & social care | 2021 |
| Corpora Winery and Trading U.K. Limited | Professional & scientific | 1995 |
| Corporate Solutions & Services Limited | Professional & scientific | 2006 |
| Cortech Design Limited | Professional & scientific | 1989 |
| Cortland Consulting Ltd | Information & communication | 2025 |
| Corvell Health Care Limited | Administrative & support | 1991 |
| Corylus Property Limited | Real estate | 2002 |
| Cosco Shipping Bulk (UK) Company Limited | Transport & logistics | 1996 |
| Cosco Shipping Crystal Logistics (UK) Company Limited | Transport & logistics | 1991 |
| Cosmeio Industries Limited | Wholesale & retail | 2025 |
| Cosmic Plant Hire Limited | Wholesale & retail | 1974 |
| Cosmos Home Improvements Limited | Wholesale & retail | 1987 |
| Costello & Sons Limited | Manufacturing | 1970 |
| Cotisens Ltd | Professional & scientific | 2002 |
| Cottis Property Holdings Limited | Professional & scientific | 1998 |
| Cottrell Civils Limited | Construction | 2007 |
| Countryside Annington (Mill Hill) Limited | Construction | 2006 |
| Countrywide Commercial (UK) Limited | Real estate | 2006 |
| Countrywide Electrical Distributors Limited | Wholesale & retail | 1994 |
| County Plumbing & Central Heating Limited | Construction | 2004 |
| Course 500 Online Academy Limited | Education | 2024 |
| Courtaulds Mews Management Company Limited | Real estate | 2004 |
| Courtesymannersrespect Limited | Health & social care | 2015 |
| Courtyard Kitchens & Home Interiors Ltd. | Construction | 2003 |
| Covermount Solutions Limited | Information & communication | 2006 |
| Covertriumph Limited | Financial services | 1987 |