| CNC1 Eco Contractors Ltd | Construction | 2021 |
| CNM Property Letting Ltd | Real estate | 2025 |
| CNS Associates Limited | Health & social care | 2015 |
| CNS Enterprises Ltd | Real estate | 2024 |
| Coates & Holland Construction Limited | Administrative & support | 2005 |
| Coates & Holland Electrical Contractors Limited | Construction | 2016 |
| Cobb Electrical (Sussex) Limited | Construction | 2018 |
| Codeshield Ltd | Information & communication | 2023 |
| Codespirit Productions Limited | Information & communication | 2017 |
| Codicote Motors Ltd | Wholesale & retail | 2018 |
| Cohere Properties Limited | Real estate | 2011 |
| Colchester Premier Business Centre Limited | Real estate | 2010 |
| Colemack Construction Limited | Construction | 2016 |
| Colinas Properties Limited | Real estate | 2026 |
| Collectorbhav Ltd | Wholesale & retail | 2026 |
| College Fields Management Company (Wolverton) Limited | Households | 2002 |
| Collins Distribution Centre Ltd | Wholesale & retail | 2020 |
| Collis Services Ltd | Construction | 2022 |
| Colour Communications Ltd | Information & communication | 2025 |
| Columbus Residents Limited | Households | 1992 |
| Come to London Limited | Real estate | 2015 |
| Comer Properties Ltd | Real estate | 2024 |
| Commercial Finance Direct Limited | Financial services | 2001 |
| Commercial Processing UK Limited | Financial services | 2004 |
| Communication Evolution Limited | Administrative & support | 2014 |
| Community Pathfinders CIC | Education | 2025 |
| Compare Repair Limited | Information & communication | 2024 |
| Complete and Utter Meltdown Ltd | Hospitality | 2026 |
| Complete Care Supplies Ltd | Other services | 2020 |
| Complete Contractors Ltd | Construction | 2014 |
| Complete Exhibition Solutions Limited | Administrative & support | 2004 |
| Complete Garden Rooms Ltd | Wholesale & retail | 2025 |
| Complete Interior Contracts Ltd | Construction | 2010 |
| Complete Property Solutions (Herts) Limited | Other services | 2016 |
| Complete Property Solutions Hatfield Limited | Other services | 2022 |
| Complete Renovation Specialist Limited | Construction | 2026 |
| Completely Different Solutions Limited | Agriculture & fishing | 1998 |
| Complus IT Ltd | Information & communication | 2015 |
| Compton Rigging Ltd | Construction | 2017 |
| Computer Room Services Ltd | Manufacturing | 2023 |
| Computerglaze Holdings Limited | Construction | 1991 |
| Comtest Wireless International Ltd | Information & communication | 2015 |
| Comtest Wireless Limited | Information & communication | 2008 |
| CONCATEN8 Ltd | Professional & scientific | 2017 |
| Concept Conversions & Refurbishments Limited | Construction | 2025 |
| Concept Research Limited | Wholesale & retail | 2004 |
| Concerto Vita Holdings Limited | Financial services | 2013 |
| Concerto Vita Limited | Financial services | 2012 |
| Concord Construction Services Limited | Professional & scientific | 2021 |
| Confident Trading Hub Limited | Administrative & support | 2026 |
| Connected Heating Solutions Ltd | Construction | 2021 |
| Connections Healthcare Ltd | Health & social care | 2020 |
| Conscious Citizen Limited | Wholesale & retail | 2021 |
| Conscious Occasions Ltd | Extraterritorial | 2020 |
| Consensus Advisory Limited | Professional & scientific | 2023 |
| CONSO4S Ltd | Information & communication | 2017 |
| Construct Maintenance Ltd | Construction | 2026 |
| Construct Services and Projects Ltd | Construction | 2025 |
| Construction Accounting Ltd | Construction | 2019 |
| Consul-It Ltd | Professional & scientific | 2018 |
| Consult Logistics Ltd | Professional & scientific | 2023 |
| Consumer Friend Ltd | Public administration | 2022 |
| Contec International Products Ltd | Transport & logistics | 2003 |
| Continental Parks Furnishing Ltd | Wholesale & retail | 2025 |
| Contour Clinic and Training Ltd | Other services | 2023 |
| Contour Cycles Ltd | Wholesale & retail | 2013 |
| Contour Fine Tooling Limited | Manufacturing | 1982 |
| Contour Planning Services Limited | Professional & scientific | 2010 |
| Contrast Events Limited | Administrative & support | 2020 |
| Conversion Detectives Ltd | Administrative & support | 2017 |
| Conway Communications (UK) Limited | Information & communication | 2000 |
| Cook's Technical Services Limited | Professional & scientific | 2018 |
| Cooks & IVY Ltd | Real estate | 2022 |
| Cooper Consulting Limited | Professional & scientific | 2015 |
| Cooper Mack Limited | Professional & scientific | 2014 |
| Copacetic LDN Ltd | Wholesale & retail | 2025 |
| Copia Holdings Ltd | Financial services | 2022 |
| Copston Associates Holdings Limited | Other services | 2018 |
| Core Strategy Limited | Administrative & support | 2025 |
| Corevision Software Limited | Information & communication | 2024 |
| Corinna Calori the Brow Lounge Ltd | Other services | 2019 |
| Corinne Freedman Limited | Information & communication | 2009 |
| Corner Property Group Limited | Real estate | 2026 |
| Cornerstone Asset Protection Limited | Administrative & support | 2021 |
| Cornerstone Fire Systems Limited | Construction | 1996 |
| Cornerstone Security Group (UK) Ltd | Construction | 2014 |
| Cornerstone Security Systems Ltd | Construction | 2009 |
| Cornerstone Youth Link Stevenage | Education | 2007 |
| Corneschi Trans Ltd | Transport & logistics | 2025 |
| Cornish & Western Housing Ltd | Financial services | 2017 |
| Cornwall Mansions Limited | Households | 2002 |
| Cornwall Mansions Management Ltd | Real estate | 2025 |
| Corrie Deane Consultancy Limited | Professional & scientific | 2015 |
| Cosma Mortgage Solutions Ltd | Financial services | 2025 |
| Cosmo International Recruitment Limited | Administrative & support | 2024 |
| Cospace Group Limited | Real estate | 2018 |
| Cospace Group MH Limited | Other services | 2018 |
| Cospace Group MK EH Limited | Real estate | 2018 |
| Cospace Group Reading QH Limited | Real estate | 2019 |
| Cospace Group SA Limited | Real estate | 2020 |