| Compare Window Market Limited | Construction | 2025 |
| Compass Asset Protection Ltd | Information & communication | 2012 |
| Compass Engineering Holdings Limited | Professional & scientific | 2014 |
| Compass Engineering Limited | Manufacturing | 1989 |
| Compass Fabrications Holdings Limited | Professional & scientific | 2014 |
| Compass Fabrications Limited | Real estate | 1999 |
| Compass One Couriers Ltd | Transport & logistics | 2024 |
| Compass Property Advisory Group Ltd | Professional & scientific | 2026 |
| Compass Systems Limited | Information & communication | 2015 |
| Compassion Care & Support Services Limited | Health & social care | 2021 |
| Compassionate Angels Care Limited | Health & social care | 2023 |
| Compassionate Care Home Care Ltd | Health & social care | 2017 |
| Complete Access Specialist Contracts Ltd | Construction | 2006 |
| Complete Beauty Ltd | Other services | 2003 |
| Complete Classroom Services Ltd | Administrative & support | 2022 |
| Complete Damp Proofing Limited | Construction | 2022 |
| Complete GAS Energy Solutions Limited | Construction | 2016 |
| Complete LEV Ltd | Professional & scientific | 2021 |
| Complete Pipework Services Limited | Construction | 2003 |
| Complete Pipework Supplies Limited | Wholesale & retail | 2006 |
| Complete Plastering Ltd | Construction | 2023 |
| Complete Project Maintenance Limited | Construction | 2019 |
| Complete Sign Installations Limited | Construction | 2024 |
| Complete Trade Services Ltd | Construction | 2026 |
| Complete Workwear Solutions Ltd | Wholesale & retail | 2012 |
| Compton Buildings Limited | Professional & scientific | 2010 |
| Compton Spares Limited | Professional & scientific | 2015 |
| Comtech Services UK Ltd | Construction | 2003 |
| Con-Tech Investments Limited | Professional & scientific | 2020 |
| Con-Tech Services Limited | Manufacturing | 1986 |
| Concept Architecture & Structural Design Ltd | Extraterritorial | 2017 |
| Concept Structural Design Ltd | Construction | 2009 |
| Concordium Holdings Ltd | Financial services | 2026 |
| Concourse Marketing Ltd | Professional & scientific | 2020 |
| Concrete Design and Detailing Limited | Professional & scientific | 2011 |
| Connect-All Properties Limited | Real estate | 2020 |
| Connectall Cabling Limited | Other services | 2012 |
| Connelly & Stacey Ltd | Construction | 2021 |
| Conroy Brook (Denby Dale) Limited | Construction | 2017 |
| Conroy Brook (Developments) Limited | Construction | 1996 |
| Conroy Brook Construction Ltd | Construction | 2004 |
| Conroy Brook Holdings Limited | Financial services | 2010 |
| Conroy Developments Limited | Professional & scientific | 2014 |
| Conroy Homes Limited | Construction | 2005 |
| Consolidated Capital Ltd | Real estate | 2016 |
| Constantia Capital Partners Limited | Health & social care | 2014 |
| Construction Industry Supplies Limited | Wholesale & retail | 2005 |
| Construction RAT Ltd | Construction | 2025 |
| Constructional Timber (Manufacturers) Limited | Construction | 1979 |
| Constructional Timber (UK) Limited | Professional & scientific | 2008 |
| Consultant Neuropsychology Services Ltd | Other services | 2019 |
| Contour Group Limited | Wholesale & retail | 2021 |
| Contract Building & Roofing Limited | Construction | 1999 |
| Contract Floors UK Limited | Construction | 2005 |
| Conway's Comfort Ltd | Real estate | 2023 |
| Conway's Groundworks Limited | Construction | 2017 |
| Conway's Property Investments Ltd | Administrative & support | 2022 |
| Conways Collective Ltd | Wholesale & retail | 2026 |
| Cool Couriers Limited | Transport & logistics | 2017 |
| Cool Cuts Group Limited | Other services | 2022 |
| Cool Kidz R US Ltd | Health & social care | 2015 |
| Coole Holdings Limited | Real estate | 2015 |
| Coole Housing Limited | Real estate | 2018 |
| Coolheat Solutions Limited | Construction | 2024 |
| Cooling & Conveying Solutions Limited | Manufacturing | 1998 |
| Coolorange Solutions Ltd | Information & communication | 2022 |
| Cooper Mortgages Ltd | Financial services | 2021 |
| Cooperson Limited | | 2013 |
| Copperfield Prime Limited | Real estate | 2021 |
| Copycat Productions Ltd | Arts & recreation | 2020 |
| Cora's Hair Salon Ltd | Other services | 2022 |
| Cordalt Limited | Construction | 2017 |
| Cordwell Engineering Limited | Manufacturing | 2025 |
| Corestra Ltd | Professional & scientific | 2026 |
| Corn Exchange Management Company (South Elmsall) Limited | Households | 2006 |
| Cornel Translogic Ltd | Transport & logistics | 2023 |
| Cornerstone Properties (Derby) Limited | Construction | 2021 |
| Corney's Ltd | Hospitality | 2025 |
| Coronation Garage Limited | Wholesale & retail | 2023 |
| Corrigo Group Limited | Financial services | 2025 |
| Cortac Limited | Construction | 1997 |
| Cortonwood Installation Services Ltd | Construction | 2011 |
| Cosgrove Property Investments Ltd | Real estate | 2025 |
| Cosy Cosmetics Ltd | Wholesale & retail | 2024 |
| Cotez Utilities Ltd | Construction | 2024 |
| Cottrell Group Holdings Ltd | Construction | 2021 |
| Couldwell Ltd | Construction | 2018 |
| Counselling Services Ltd | Other services | 2019 |
| Country Club (Barnsley) Limited | Hospitality | 2024 |
| Couriers Delivery by NEC Limited | Transport & logistics | 2025 |
| Course Group Limited | Financial services | 2023 |
| Courtyard Marketing Limited | Professional & scientific | 2016 |
| Courvix Ltd | Information & communication | 2021 |
| Covertop Limited | Wholesale & retail | 2000 |
| COW Developments Limited | Real estate | 2023 |
| Cozyfloor Insulation Ltd | Construction | 2023 |
| CPC Contemporary Professional Construction Limited | Construction | 2016 |
| Cpdas Ltd | Administrative & support | 2020 |
| CPI Attero Limited | Manufacturing | 2013 |
| CPI Holdings (UK) Limited | Financial services | 2010 |