| Clark and Carter Restorations Limited | Wholesale & retail | 2001 |
| Clarke Kitchens Ltd | Construction | 2022 |
| Clarks Car Storage Limited | Transport & logistics | 2020 |
| Classic Launderette Ltd | Administrative & support | 2025 |
| Classic RUG Care Limited | Administrative & support | 1997 |
| Clean Air Systems & Installations Limited | Construction | 2002 |
| Clean Air Trustees Limited | Professional & scientific | 2025 |
| Clean Services Ltd | Construction | 2020 |
| Clearview Services Holdings Limited | Financial services | 2023 |
| Clerro Ltd | Information & communication | 2026 |
| Click Genius Ltd | Professional & scientific | 2022 |
| Clientweb Limited | Information & communication | 2003 |
| Clive Brookson Ltd | Wholesale & retail | 2020 |
| Clive Saych & SON Limited | Construction | 2009 |
| Clockwork Operational Solutions Limited | Professional & scientific | 2025 |
| Cloud Coalesce Limited | Information & communication | 2026 |
| Cloud Works Limited | Information & communication | 2022 |
| Cluetopia Braintree Ltd | Arts & recreation | 2024 |
| CM Build Ltd | Construction | 2019 |
| CM Joinery Works Ltd | Manufacturing | 2020 |
| CM Medical Personnel Limited | Health & social care | 2022 |
| CM Thompson Limited | Real estate | 2019 |
| CM7 Braintree Ltd | Hospitality | 2025 |
| CM7 Sign & Print Ltd | Construction | 2026 |
| CM7 Sign Install Ltd | Construction | 2026 |
| Cmec UK & Mena Limited | Administrative & support | 2019 |
| CML Building & Carpentry Ltd | Construction | 2015 |
| Cmsn Investments Ltd | Hospitality | 2025 |
| CNC 2010 Ltd | Other services | 2010 |
| Coaster Consulting Ltd | Information & communication | 2021 |
| Coaster Production Ltd | Arts & recreation | 2021 |
| Cobalt Marine Consultancy Ltd | Information & communication | 2019 |
| Coda Systems Limited | Wholesale & retail | 1980 |
| Code Rods Limited | Manufacturing | 2023 |
| Coded Vision Design Ltd | Information & communication | 2013 |
| Codedeck Consulting Ltd | Information & communication | 2019 |
| Coffee House in the Gardens Ltd | Hospitality | 2025 |
| Coffee Lane Limited | Hospitality | 2024 |
| Coggeshall Investment Limited | Real estate | 2015 |
| Coker Group Holdings Limited | Professional & scientific | 2016 |
| Cole Aviation Limited | Administrative & support | 1995 |
| Coleman Construction & Utilities Limited | Construction | 2000 |
| Coleman Corp Limited | Information & communication | 2011 |
| Coles & Hills Ltd | Construction | 2024 |
| Collabridge Limited | Professional & scientific | 1979 |
| Collared Limited | Wholesale & retail | 2015 |
| Collett Interiors Ltd | Construction | 2016 |
| Collier Mechanical Ltd | Construction | 2023 |
| Collings Limited | Hospitality | 2020 |
| Colne Valley Groundcare Ltd | Administrative & support | 2009 |
| Colne Valley Security Ltd | Administrative & support | 2017 |
| Color Trix Ltd | Information & communication | 2019 |
| Coloured by Ltd | Manufacturing | 2022 |
| Common Flipside Ltd | Information & communication | 2021 |
| Communications Solution Providers Limited | Information & communication | 1999 |
| Complete Air Conditioning Services Ltd | Energy | 2025 |
| Complete Care Partnership Ltd | Health & social care | 2024 |
| Complete Conscious Care Limited | Health & social care | 2025 |
| Complete Health and Fitness Limited | Arts & recreation | 2001 |
| Complete Hotels Services Ltd | Professional & scientific | 2008 |
| Complete Sports Services Limited | Manufacturing | 2009 |
| Completehotels Limited | Hospitality | 2004 |
| Compliance Fire Ltd | Public administration | 2020 |
| Compliance First Lettings Ltd | Real estate | 2026 |
| Compliance Labelling Solutions Holdings Limited | Administrative & support | 2015 |
| Compliance Labelling Solutions Limited | Manufacturing | 2000 |
| Concept Carpentry and Services Limited | Construction | 2018 |
| Concept Press Limited | Extraterritorial | 2013 |
| Concept Van Conversions Ltd | Manufacturing | 2022 |
| Connect Exec Limited | Administrative & support | 2018 |
| Connect-Green Ltd | Construction | 2010 |
| Connectix Limited | Manufacturing | 1993 |
| Connelly Associates Limited | Professional & scientific | 2008 |
| Connor Lodge Ltd | Health & social care | 2026 |
| Conserve Media Productions Limited | Information & communication | 2024 |
| Consolis Systems Limited | Information & communication | 2007 |
| Constance & Carraways Management RTM Company Limited | Households | 2004 |
| Construction Supply Hub Ltd | Information & communication | 2015 |
| Continuous Hinge Co Ltd | Professional & scientific | 2001 |
| Continuous Piano Hinge Company Limited | Manufacturing | 1993 |
| Contract Drive Ltd | Transport & logistics | 2023 |
| Contracts Support Services Limited | Administrative & support | 1994 |
| Cook Brothers Limited | Manufacturing | 2006 |
| Cool Tech Solutions UK Ltd | Information & communication | 2025 |
| Cooper Bros.(Gt.Oakley)Limited | Agriculture & fishing | 1958 |
| Cooper Bros.(Wix)Limited | Agriculture & fishing | 1958 |
| Coops IT Services Limited | Information & communication | 2012 |
| Coote and Sons Ltd | Real estate | 2021 |
| Cootes (Highwoods) Ltd | Wholesale & retail | 2013 |
| Copper Birch Limited | Professional & scientific | 2014 |
| Coral House Management Company Limited | Real estate | 1984 |
| Core Servicing Limited | Information & communication | 2014 |
| Coreline Surveying & Consulting Limited | Construction | 2026 |
| Coretechsolutions IT Ltd | Information & communication | 2016 |
| Corndon Hill Farm Ltd | Agriculture & fishing | 2025 |
| Cornerstone Classic Cars Limited | Wholesale & retail | 2025 |
| Cornwell Construction Limited | Construction | 2010 |
| Cosec Corporate Services Ltd | Financial services | 2018 |
| Cosmetic Surgery Services Ltd | Professional & scientific | 2021 |
| Cosmo Twins Ltd | Wholesale & retail | 2013 |